Projection lens system and image projection device

ABSTRACT

A projection lens system that projects an image of a reduction side into a magnification side includes a diaphragm, a plurality of positive lenses, and a plurality of negative lenses. The plurality of positive lenses include a first positive lens closer to the magnification side than the diaphragm is and closest to the diaphragm, a second positive lens second closest to the diaphragm after the first positive lens on the magnification side, a third positive lens closer to the reduction side than the diaphragm is and closest to the diaphragm. The plurality of negative lenses include a first negative lens closer to the magnification side than the diaphragm is and closest to the diaphragm, and a second negative lens closer to the reduction side than the diaphragm is and closest to the diaphragm. The lenses have transmittances larger than threshold values, respectively.

CROSS-REFERENCE OF RELATED APPLICATIONS

This application is a continuation of International Patent Application No. PCT/JP2018/044810, filed on Dec. 6, 2018, which claims the benefit of Japanese Patent Application No. 2017-243055, filed on Dec. 19, 2017, the contents all of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a projection lens system that projects an image of a reduction side into a magnification side, and an image projection device including the projection lens system.

BACKGROUND ART

PTL 1 discloses an optical system for successfully correcting chromatic aberrations and reducing a shift in focus position due to a temperature change in an image projection device and an imaging device. In the optical system of PTL 1, at least two positive lenses in which the Abbe number, anomalous dispersion property, rate of change in refractive index with respect to temperature changes, and the like are set in appropriate ranges are disposed closer to the reduction side than a diaphragm. As a result, the shift in the focus position caused by the change in refractive index due to the temperature change can be reduced, while the axial chromatic aberration is successfully corrected by increasing the width of an axial light flux. PTL 1 describes that a lamp used as a light source is a cause of high temperature in the image projection device.

CITATION LIST Patent Literature

-   PTL 1: Unexamined Japanese Patent Publication No. 2011-053663

SUMMARY

The present disclosure provides a projection lens system and an image projection device that can improve the image quality of an image when the brightness of the image projection device is increased.

A projection lens system according to the present disclosure is a lens system that projects an image of a reduction side into a magnification side. The projection lens system includes a diaphragm, a plurality of positive lenses, and a plurality of negative lenses. The plurality of positive lenses include a first positive lens that is closer to the magnification side than the diaphragm is and is closest to the diaphragm, a second positive lens that is second closest to the diaphragm after the first positive lens on the magnification side, and a third positive lens that is closer to the reduction side than the diaphragm is and is closest to the diaphragm. The first to third positive lenses satisfy following conditions (1) to (3). The plurality of negative lenses include a first negative lens that is closer to the magnification side than the diaphragm is and is closest to the diaphragm and a second negative lens that is closer to the reduction side than the diaphragm is and is closest to the diaphragm. The first and second negative lenses satisfy following conditions (4) to (6). At least one positive lens of the first to third positive lenses satisfies following conditions (7) and (8), Tp1>99%  (1) Tp2>99%  (2) Tp3>99%  (3) Tn1>99%  (4) Tn2>99%  (5) αn1<100×10⁻⁷[/° C.]  (6) dn/dt<−4.5×10⁻⁶  (7) |fp/fw|>1.3  (8)

where

Tp1 indicates an internal transmittance of light having a wavelength of 460 nm when a lens material of the first positive lens has a thickness of 10 mm,

Tp2 indicates an internal transmittance of light having a wavelength of 460 nm when a lens material of the second positive lens has the thickness mentioned above,

Tp3 indicates an internal transmittance of light having a wavelength of 460 nm when a lens material of the third positive lens has the thickness mentioned above,

Tn1 indicates an internal transmittance of light having a wavelength of 460 nm when a lens material of the first negative lens has the thickness mentioned above,

Tn2 indicates an internal transmittance of light having a wavelength of 460 nm when a lens material of the second negative lens has the thickness mentioned above,

αn1 indicates a linear expansion coefficient of the lens material of the first negative lens at room temperature,

dn/dt indicates a temperature coefficient of a relative refractive index of a lens material of the at least one positive lens at room temperature,

fp indicates a focal length of the at least one positive lens, and

fw indicates a focal length at the wide-angle end of a whole system.

An image projection device according to the present disclosure includes the projection lens system described above and an image forming element. The image forming element forms an image.

According to the projection lens system and the image projection device according to the present disclosure, it is possible to improve the image quality of an image when the brightness of the image projection device is increased.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating an image projection device according to a first exemplary embodiment of the present disclosure.

FIG. 2 is a lens arrangement diagram in various states of a projection lens system according to a first example.

FIG. 3 is an aberration diagram illustrating longitudinal aberrations of the projection lens system according to the first example.

FIG. 4 is a table illustrating sufficiency of various conditions in the projection lens system according to the first example.

FIG. 5 is a lens arrangement diagram in various states of a projection lens system according to a second example.

FIG. 6 is an aberration diagram illustrating longitudinal aberrations of the projection lens system according to the second example.

FIG. 7 is a table illustrating sufficiency of various conditions in the projection lens system according to the second example.

FIG. 8 is a lens arrangement diagram in various states of a projection lens system according to a third example.

FIG. 9 is an aberration diagram illustrating longitudinal aberrations of the projection lens system according to the third example.

FIG. 10 is a table illustrating sufficiency of various conditions in the projection lens system according to the third example.

FIG. 11 is a lens arrangement diagram of a projection lens system according to a fourth example.

FIG. 12 is an aberration diagram illustrating longitudinal aberrations of the projection lens system according to the fourth example.

FIG. 13 is an optical path diagram illustrating an optical path of a ray in the projection lens system according to the fourth example.

FIG. 14 is a table illustrating sufficiency of various conditions in the projection lens system according to the fourth example.

FIG. 15 is a lens arrangement diagram of a projection lens system according to a fifth example.

FIG. 16 is an aberration diagram illustrating longitudinal aberrations of the projection lens system according to the fifth example.

FIG. 17 is an optical path diagram illustrating an optical path of a ray in the projection lens system according to the fifth example.

FIG. 18 is a table illustrating sufficiency of various conditions in the projection lens system according to the fifth example.

FIG. 19 is a lens arrangement diagram of a projection lens system according to a sixth example.

FIG. 20 is an aberration diagram illustrating longitudinal aberrations of the projection lens system according to the sixth example.

FIG. 21 is an optical path diagram illustrating an optical path of a ray in the projection lens system according to the sixth example.

FIG. 22 is a table illustrating sufficiency of various conditions in the projection lens system according to the sixth example.

FIG. 23 is a lens arrangement diagram in various states of a projection lens system according to a seventh example.

FIG. 24 is an aberration diagram illustrating longitudinal aberrations of the projection lens system according to the seventh example.

FIG. 25 is a table illustrating sufficiency of various conditions in the projection lens system according to the seventh example.

FIG. 26 is a lens arrangement diagram in various states of a projection lens system according to an eighth example.

FIG. 27 is an aberration diagram illustrating longitudinal aberrations of the projection lens system according to the eighth example.

FIG. 28 is a table illustrating sufficiency of various conditions in the projection lens system according to the eighth example.

FIG. 29 is a lens arrangement diagram in various states of a projection lens system according to a ninth example.

FIG. 30 is an aberration diagram illustrating longitudinal aberrations of the projection lens system according to the ninth example.

FIG. 31 is a table illustrating sufficiency of various conditions in the projection lens system according to the ninth example.

DESCRIPTION OF EMBODIMENTS

Exemplary embodiments will be described below in detail with reference to the drawings as appropriate. Here, excessively detailed description will be omitted in some cases. For example, detailed description of already well-known matters and duplicated description of the substantially same configurations will be omitted in some cases. This is to prevent the following description from becoming unnecessarily redundant, thereby facilitating the understanding of those skilled in the art.

Here, the applicant provides the accompanying drawings and the following description such that those skilled in the art can fully understand the present disclosure, and therefore, does not intend to limit the subject matters described in the claims by the accompanying drawings and the following description.

First Exemplary Embodiment

Hereinafter, a first exemplary embodiment of a projection lens system and an image projection device according to the present disclosure will be described with reference to the drawings.

1. Outline

An outline of an image projection device including a projection lens system according to the first exemplary embodiment of the present disclosure will be described with reference to FIG. 1. FIG. 1 is a block diagram illustrating image projection device 1 according to the present exemplary embodiment.

Image projection device 1 according to the present exemplary embodiment is, for example, a high brightness projector having a light output of 20,000 lumens or more. In image projection device 1, as illustrated in FIG. 1, image light 3 showing various images 2 is generated by using image forming element 11 and the like, and image light 3 enters projection lens system PL. Projection lens system PL emits projection light 35 so as to magnify image 2 of entering image light 3. Projection light 35 from projection lens system PL projects projection image 20 obtained by magnifying image 2 on external screen 4 or the like.

In image projection device 1 as described above, it is required to increase brightness so as to project projection image 20 more brightly. In increasing the brightness of image projection device 1, it is assumed that image quality of projection image 20 is degraded by following factors.

That is, it is assumed in image projection device 1 that, when image light 3 having high brightness travels in projection lens system PL, a significant temperature change occurs in particular lens element Ln near diaphragm A or the like in projection lens system PL by concentration of rays or the like. The temperature change of lens element Ln changes a shape and a refractive index of lens element Ln, and thus may have various influences on performance of projection lens system PL, such as a shift in focus position, occurrence of spherical aberrations, and a variation in back focus.

In addition, the heat distribution of lens element Ln due to image light 3 may occur either uniformly or locally. It is considered that an influence of heat, such as a shift direction of the focus position, in a uniform case is different from that in a local case. As described above, in increasing the brightness of image projection device 1, it is assumed that the performance of projection lens system PL becomes unstable due to the influence of heat according to the brightness of image 2 to be projected, and the image quality of projection image 20 is degraded.

Consequently, in the present exemplary embodiment, projection lens system PL is configured so as to reduce the influence of heat due to image light 3 with high brightness. As a result, it is possible to reduce the influence of heat in increasing the brightness of image projection device 1, stabilize the performance of projection lens system PL, and improve the image quality of projection image 20.

2. About Image Projection Device

A configuration of image projection device 1 according to the present exemplary embodiment will be described below with reference to FIG. 1.

As illustrated in FIG. 1, image projection device 1 according to the present exemplary embodiment includes light source 10, image forming element 11, transmission optical system 12, and projection lens system PL. Image projection device 1 is configured with, for example, a DLP system. The light output of image projection device 1 may be more than or equal to 30,000 lumens.

Light source 10 is, for example, a laser light source. Light source 10 includes, for example, a blue LD (semiconductor laser) element and has a peak wavelength near 450 nm. Light source 10 emits white illumination light 30 by, for example, combining various colors. Illumination light 30 is irradiated to image forming element 11 via transmission optical system 12 with a uniform illuminance distribution. Light source 10 may include a Koehler illumination optical system.

Image forming element 11 is, for example, a digital mirror device (DMD). Image forming element 11 has, for example, an image forming surface including a mirror element for each pixel, and forms image 2 on the image forming surface based on an external video signal or the like. Image forming element 11 spatially modulates illumination light 30 on the image forming surface to generate image light 3. Image light 3 has directionality for each pixel on the image forming surface, for example.

Image projection device 1 may include a plurality of image forming elements 11 such as three chips corresponding to RGB. Image forming element 11 is not limited to the DMD and may be, for example, a liquid crystal element. In this case, image projection device 1 may be configured with a 3LCD system or an LCOS system.

Transmission optical system 12 includes a translucent optical element and the like, and is disposed between image forming element 11 and projection lens system PL. Transmission optical system 12 guides illumination light 30 from light source 10 to image forming element 11. Further, transmission optical system 12 guides image light 3 from image forming element 11 to projection lens system PL. Transmission optical system 12 may include various optical elements such as a total internal reflection (TIR) prism, a color separation prism, a color combination prism, an optical filter, a parallel plate glass, a crystal low-pass filter, and an infrared cut filter. Hereinafter, the optical element in transmission optical system 12 is referred to as “back glass” in some cases.

Projection lens system PL is mounted on image projection device 1, for example, as a module. Hereinafter, in projection lens system PL, a side facing outside of image projection device 1 is referred to as a “magnification side”, and a side opposite to the magnification side is referred to as a “reduction side”. Various back glasses of transmission optical system 12 are disposed on the reduction side of projection lens system PL.

Projection lens system PL includes a plurality of lens elements Ln and diaphragm A. A number of lens elements Ln is, for example, more than or equal to 15. This makes it possible to successfully correct various aberrations in projection lens system PL. Diaphragm A is, for example, an aperture diaphragm. In projection lens system PL, an aperture degree of diaphragm A is fixed in advance to, for example, an open state. Projection lens system PL may be incorporated in image projection device 1 without being modularized. Hereinafter, details of projection lens system PL according to the present exemplary embodiment will be described.

3. About Projection Lens System

In the first exemplary embodiment, first to third examples in which projection lens system PL configuring a negative-lead zoom lens system will be described as a specific example. The negative-lead zoom lens system is a lens system that includes a plurality of lens groups that move during zooming and in which a lens group on a most magnification side has a negative power.

3-1. First Example

Projection lens system PL1 of the first example will be described with reference to FIGS. 2 to 3.

FIG. 2 is a lens arrangement diagram in various states of projection lens system PL1 according to the first example. Following lens arrangement diagrams each illustrate an arrangement of various lenses when a whole system such as projection lens system PL1 is focused at 4,000 mm. A left side in the figure is a magnification side or object side of the whole system. A right side in the figure is a reduction side or image side of the whole system. In each figure, a position of image plane S is illustrated on a rightmost side, that is, on the reduction side. Image plane S corresponds to the image forming surface of image forming element 11.

FIG. 2(a) is a lens arrangement diagram at a wide-angle end of projection lens system PL1 according to the first example. FIG. 2 (b) is a lens arrangement diagram at an intermediate position of projection lens system PL1 according to the first example. FIG. 2(c) is a lens arrangement diagram at a telephoto end of projection lens system PL1 according to the first example. The wide-angle end means a shortest focal length state where the whole system has shortest focal length fw. The intermediate position means an intermediate focal length state between the wide-angle end and the telephoto end. The telephoto end means a longest focal length state where the whole system has longest focal length ft. Based on focal length fw at the wide-angle end and focal length ft at the telephoto end, a focal length at the intermediate position is defined as fm=√(fw×ft).

Line arrows indicated between FIG. 2(a) and FIG. 2(b) are lines obtained by connecting positions of lens groups at the wide-angle end, the intermediate position, and the telephoto end in this order from a top of the figure. The wide-angle end and the intermediate position, and the intermediate position and the telephoto end are simply connected by straight lines, which is different from an actual movement of each lens group. Symbols (+) and (−) attached to reference signs of the respective lens groups indicate positive and negative of the power of each lens group.

Projection lens system PL1 of the first example includes 18 lens elements L1 to L18 constituting three lens groups G1 to G3. As illustrated in FIG. 2(a), first, second, and third lens groups G1, G2, G3 are arranged in order from the magnification side to the reduction side of projection lens system PL1. Projection lens system PL1 functions as a zoom lens system by moving each of first to third lens groups G1 to G3 along an optical axis of projection lens system PL1 during zooming.

In projection lens system PL1, first to eighteenth lens elements L1 to L18 are arranged in order from the magnification side to the reduction side. Each of first to eighteenth lens elements L1 to L18 configures a positive lens or a negative lens. The positive lens has a biconvex shape or a positive meniscus shape and thus has a positive power. The negative lens has a biconcave shape or a negative meniscus shape and thus has a negative power.

First lens group G1 includes first to seventh lens elements L1 to L7, and has a negative power. First lens element L1 has a negative meniscus shape, and is arranged with its convex surface facing the magnification side. Second lens element L2 has a biconvex shape. Third lens element L3 has a positive meniscus shape, and is arranged with its convex surface facing the magnification side. Fourth lens element L4 has a negative meniscus shape, and is arranged with its convex surface facing the magnification side. Fifth lens element L5 has a negative meniscus shape, and is arranged with its convex surface facing the magnification side. Sixth lens element L6 has a biconcave shape. Seventh lens element L7 has a biconvex shape.

Second lens group G2 includes eighth to tenth lens elements L8 to L10, and has a positive power. Eighth lens element L8 has a positive meniscus shape, and is arranged with its convex surface facing the magnification side. Ninth lens element L9 has a negative meniscus shape, and is arranged with its convex surface facing the magnification side. Tenth lens element L10 has a biconvex shape.

Third lens group G3 includes eleventh to eighteenth lens elements L11 to L18, and has a positive power. Diaphragm A is disposed on the magnification side of eleventh lens element L11. Eleventh lens element L11 has a biconcave shape. Twelfth lens element L12 has a biconvex shape. Thirteenth lens element L13 has a positive meniscus shape, and is arranged with its convex surface facing the reduction side. Fourteenth lens element L14 has a biconvex shape. Fifteenth lens element L15 has a biconcave shape. Sixteenth lens element L16 has a biconvex shape. Seventeenth lens element L17 has a negative meniscus shape, and is arranged with its convex surface facing the reduction side. Eighteenth lens element L18 has a biconvex shape.

FIGS. 2(a) to 2(c) illustrate, as an example of transmission optical system 12, three back glasses L19, L20, L21 arranged between eighteenth lens element L18 on the most reduction side in projection lens system PL1 and image plane S. Back glasses L19 to L21 are, for example, various prisms, filters, cover glasses, and the like. In each figure, back glasses L19 to L21 for one image plane S corresponding to one image forming element 11 are illustrated for convenience of description. Projection lens system PL1 can be used for various transmission optical systems 12 when a plurality of image forming elements 11 are used.

Projection lens system PL1 constitutes a substantially telecentric system on the reduction side to which light from image plane S enters through back glasses L19 to L21. It is thus possible to reduce a color shift and the like due to a coating of a prism in transmission optical system 12. Further, the light from image plane S of image forming element 11 can be efficiently taken into projection lens system PL1.

FIG. 3 is an aberration diagram illustrating various longitudinal aberrations of projection lens system PL1 according to the first example. Following aberration diagrams exemplify various longitudinal aberrations in a focused state at 4,000 mm.

FIG. 3(a) illustrates aberrations at the wide-angle end of projection lens system PL1 according to the first example. FIG. 3(b) illustrates aberrations at the intermediate position of projection lens system PL1 according to the first example. FIG. 3(c) illustrates aberrations at the telephoto end of projection lens system PL1 according to the first example. FIGS. 3(a), 3(b), 3(c) each include a spherical aberration diagram showing a spherical aberration on horizontal axis “SA (mm)”, an astigmatism diagram showing an astigmatism on horizontal axis “AST (mm)”, and a distortion aberration diagram showing a distortion aberration on horizontal axis “DIS (%)” in this order from the left side in the respective figures.

In each spherical aberration diagram, vertical axis “F” represents an F number. Also, a solid line denoted by “d-line” in the figures indicates properties of a d-line. A broken line denoted by “F-line” indicates properties of an F-line. A broken line denoted by “C-line” indicates properties of a C-line. In the respective astigmatism diagrams and the respective distortion aberration diagrams, vertical axis “H” indicates an image height. In addition, a solid line denoted by “s” in the figures indicates properties of a sagittal plane. A broken line denoted by “m” indicates properties of a meridional plane.

The aberrations in various states illustrated in FIGS. 3(a), 3(b), 3(c) are based on a first numerical example in which projection lens system PL1 of the first example is specifically implemented. The first numerical example of projection lens system PL1 will be described later.

3-2. About Measures for Heat in Increasing Brightness

Using projection lens system PL1 of the first example described above, measures for heat of projection lens system PL1 in increasing the brightness of image projection device 1 according to the present exemplary embodiment will be described with reference to FIG. 4. FIG. 4 is a table illustrating sufficiency of various conditions in projection lens system PL1 according to the first example.

The table illustrated in FIG. 4 shows which of all lens elements L1 to L18 in projection lens system PL1 of the first example satisfies following conditions (1) to (11). The symbol “∘” in items for each lens indicates that the corresponding condition is satisfied, and the blank indicates that the corresponding condition is not satisfied. In addition, the symbol “/” indicates that the lens is not a target lens for determining the corresponding condition from the viewpoint of the power of the lens or the like.

FIG. 4 also shows various parameters related to conditions (1) to (11). The various parameters include α, T (460 nm), vd, and dn/dt, which will be described later. Regarding the power of the lens, the positive lens is denoted by “P”, and the negative lens is denoted by “N”. Further, lens materials of the lens elements L1 to L18 are also shown.

In the present exemplary embodiment, it is configured that a particular lens that is assumed to be easily affected by heat of image light 3 in image projection device 1 and easily affect the performance of projection lens system PL1 satisfies following conditions (1) to (6). The particular lens is located near diaphragm A in projection lens system PL1, and includes first, second and third positive lenses and first and second negative lenses.

The first positive lens is a positive lens that is closer to the magnification side than diaphragm A is and is the closest to the diaphragm A among all the positive lenses in projection lens system PL1. In the first example, as illustrated in FIG. 2, diaphragm A is disposed between tenth lens element L10 and eleventh lens element L11. Consequently, tenth lens element L10 of the first example is the first positive lens in projection lens system PL1 and satisfies following condition (1).

Condition (1) is expressed by a following inequality. Tp1>99%  (1)

Here, Tp1 indicates an internal transmittance obtained by removing a surface reflection loss from a transmittance at which light having a wavelength of 460 nm passes through a lens material of the first positive lens having a thickness of 10 mm. FIG. 4 shows internal transmittance T (460 nm) of light having a wavelength of 460 nm when a lens material of each of lens elements L1 to L18 has a thickness of 10 mm. In general, the lens material is more likely to absorb energy of light having a shorter wavelength, and a light source having a particularly strong peak intensity for blue light is usually used in an image projection device. A reference transmittance is thus set to the wavelength mentioned above.

According to condition (1), it is possible to achieve high internal transmittance Tp1 of the first positive lens where rays may be concentrated near diaphragm A and reduce energy absorbed by the first positive lens when a ray passes through the first positive lens. If internal transmittance Tp1 of the first positive lens is less than a lower limit value of condition (1), that is, 99%, the energy absorbed by the first positive lens becomes large, and the influence of heat is excessively exerted on the first positive lens.

The second positive lens is a positive lens that is closer to the magnification side than diaphragm A is and is the second closest to diaphragm A after the first positive lens, among all the positive lenses in projection lens system PL1. In the first example, the positive lens that is the second closest to diaphragm A after tenth lens element L10 on the magnification side is eighth lens element L8, as illustrated in FIG. 2. Consequently, eighth lens element L8 of the first example is the second positive lens in projection lens system PL1 as illustrated in FIG. 4, and satisfies following condition (2).

Condition (2) is expressed by the following inequality. Tp2>99%  (2)

Here, Tp2 indicates the internal transmittance of light having a wavelength of 460 nm when a lens material of the second positive lens has a thickness of 10 mm, like the internal transmittance of the first positive lens. If internal transmittance Tp2 of the second positive lens is less than the lower limit value of condition (2), the energy absorbed by the second positive lens becomes large, and the influence of heat is excessively exerted on the second positive lens.

The third positive lens is a positive lens that is closer to the reduction side than diaphragm A is and is the closest to diaphragm A among all the positive lenses in projection lens system PL1. In the first example, since eleventh lens element L11 adjacent to the reduction side of diaphragm A is a negative lens, the positive lens closest to diaphragm A on the reduction side is twelfth lens element L12. Consequently, twelfth lens element L12 of the first example is the third positive lens in projection lens system PL1 as illustrated in FIG. 4, and satisfies following condition (3).

Condition (3) is expressed by the following inequality. Tp3>99%  (3)

Here, Tp3 indicates the internal transmittance of light having a wavelength of 460 nm when a lens material of the third positive lens has a thickness of 10 mm, like the internal transmittance of the first positive lens. If internal transmittance Tp3 of the third positive lens is less than the lower limit value of condition (3), the energy absorbed by the third positive lens becomes large, and the influence of heat is excessively exerted on the third positive lens.

The first negative lens is a negative lens that is closer to the magnification side than diaphragm A is and is the closest to diaphragm A among all the negative lenses in projection lens system PL1. In the first example, since tenth lens element L10 adjacent to the magnification side of diaphragm A is a positive lens, the negative lens closest to diaphragm A on the magnification side is ninth lens element L9. Consequently, ninth lens element L9 of the first example is the first negative lens in projection lens system PL1 as illustrated in FIG. 4, and satisfies following condition (4).

Condition (4) is expressed by the following inequality. Tn1>99%  (4)

Here, Tn1 indicates the internal transmittance of light having a wavelength of 460 nm when a lens material of the first negative lens has a thickness of 10 mm, like the internal transmittance of the first positive lens. The first negative lens satisfies following condition (4). If internal transmittance Tn1 of the first negative lens is less than a lower limit value of condition (4), the energy absorbed by the first negative lens becomes large, and the influence of heat is excessively exerted on the first negative lens.

The second negative lens is a negative lens that is closer to the reduction side than diaphragm A is and is the closest to diaphragm A among all the negative lenses in projection lens system PL1. In the first example, eleventh lens element L11 is the second negative lens in projection lens system PL1 as illustrated in FIG. 4, and satisfies following condition (5).

Condition (5) is expressed by the following inequality. Tn2>99%  (5)

Here, Tn2 indicates the internal transmittance of light having a wavelength of 460 nm when a lens material of the second negative lens has a thickness of 10 mm, like the internal transmittance of the first positive lens. If internal transmittance Tn2 of the second negative lens is less than the lower limit value of condition (5), the energy absorbed by the second negative lens becomes large, and the influence of heat is excessively exerted on the second negative lens.

According to conditions (2) to (5), the energy absorbed from a ray can be reduced and the influence of heat in projection lens PL1 can also be reduced in the second and third positive lenses and the first and second negative lenses, as in the case of condition (1).

Condition (6) is expressed by the following inequality. αn1<100×10⁻⁷[/° C.]  (6)

Here, αn1 indicates a linear expansion coefficient of the lens material of the first negative lens at room temperature. The room temperature ranges from 20° C. to 30° C., for example. In FIG. 4, linear expansion coefficient α of the lens material of each of lens elements L1 to L18 at room temperature is shown in a unit [10⁻⁷/° C.].

According to condition (6), in the negative lenses where a sensitive shift in focus position due to a temperature change is supposed to occur, a change in the shape of the first negative lens which easily rises in temperature particularly near diaphragm A can be reduced, and thus performance of projection lens system PL1 can be stabilized. If linear expansion coefficient α of the first negative lens exceeds an upper limit value of condition (6), the shape of the first negative lens is easily changed locally due to the rise in the temperature of the first negative lens, and the influence of heat is excessively exerted on the first negative lens.

Further, it is configured in the present exemplary embodiment that at least one of the first to third positive lenses satisfies following conditions (7) and (8). In projection lens system PL1 of the first example, as illustrated in FIG. 4, two lens elements, that is, eighth lens element L8 (second positive lens) and tenth lens element L10 (first positive lens) satisfy conditions (7) and (8).

Condition (7) is expressed by the following inequality. dn/dt<−4.5×10⁻⁶  (7)

Here, dn/dt indicates a temperature coefficient of a relative refractive index of the lens material of the positive lens at room temperature. In FIG. 4, temperature coefficient dn/dt of the relative refractive index is shown in the unit [10⁻⁶].

In a positive lens having a negative temperature coefficient of the refractive index, the influence of a change in shape and the influence of a change in refractive index may be offset when the focus position is shifted due to a local temperature change. According to condition (7), the influence of heat on the change in image 2 to be projected can be reduced by the offset described above, and a variation in the image quality of projection image 20 can be reduced. If temperature coefficient dn/dt of the relative refractive index of the positive lens exceeds the upper limit value of condition (7), it is difficult to offset the influence of the change in the shape of the positive lens due to the local change in temperature by the influence of the change in refractive index.

Condition (8) is expressed by the following inequality. |fp/fw|>1.3  (8)

Here, fp indicates a focal length of one negative lens. As described above, fw indicates the focal length at the wide-angle end of the whole system.

According to condition (8), it is possible to reduce the influence of heat by achieving long focal length fp of the positive lens and thus weakening the power of the positive lens. If the positive lens has a value less than the lower limit value of condition (8), the focus position or the like may sensitively vary depending on image 2 to be projected. With conditions (7), (8), it is possible to reduce the influence of heat on the first to third positive lenses, which easily affects the performance of projection lens system PL1, thus stabilizing the performance of projection lens system PL1.

Moreover, in the present exemplary embodiment, at least one positive lens may satisfy condition (9). In projection lens system PL1 of the first example, as illustrated in FIG. 4, four lens elements, that is, second lens element L2, third lens element L3, twelfth lens element L12, and thirteenth lens element L13 satisfy condition (9).

Condition (9) is expressed by the following inequality. νp<40  (9)

Here, νp indicates the Abbe number of the lens material of the positive lens. As illustrated in FIG. 4 for example, Abbe number vd based on the d line can be adopted as Abbe number vp.

In general, a lens material having a higher Abbe number tends to have a higher transmittance and is thermally advantageous. However, it is difficult to successfully correct the chromatic aberration of projection lens system PL1 only with the positive lens having a value that exceeds the upper limit value of condition (9). By including a positive lens that satisfies condition (9) in projection lens system PL1, it is possible to successfully correct the chromatic aberration while achieving heat resistance when the brightness is increased. In particular, the chromatic aberration can be successfully corrected when a high zoom or a wide angle is achieved in projection lens system PL1. Abbe number νp of at least one positive lens is preferably smaller than 36.

Moreover, in the present exemplary embodiment, at least one negative lens may satisfy following condition (10). In projection lens system PL1 of the first example, as illustrated in FIG. 4, two lenses, that is, first lens element L1 and seventeenth lens element L17 satisfy condition (10).

Condition (10) is expressed by the following inequality. νn<40  (10)

Here, νn indicates the Abbe number of the lens material of the negative lens, like Abbe number νp of the positive lens.

If all the negative lenses have a value exceeding the upper limit value of condition (10), it becomes difficult to successfully correct the chromatic aberration in projection lens system PL1. According to condition (10), it is possible to successfully correct the chromatic aberration particularly in a case of a high zoom or a wide angle while achieving the heat resistance when the brightness is increased. It is preferable that Abbe number νn of at least one negative lens is smaller than 36.

Moreover, in the present exemplary embodiment, at least four positive lenses may satisfy following condition (11). In projection lens system PL1 of the first example, as illustrated in FIG. 4, five lens elements, that is, eighth lens L8, tenth lens element L10, fourteenth lens element L14, sixteenth lens element L16, and eighteenth lens element L18 satisfy condition (11).

Condition (11) is expressed by the following inequality. dn/dt<−4.5×10⁻⁶  (11)

Here, dn/dt indicates the temperature coefficient of the relative refractive index of the lens material of the positive lens at room temperature, as in condition (7).

According to condition (11), the influence of a change in shape due to a local temperature change and the influence of a change in refractive index are offset, and four or more positive lenses that are hardly affected by the influence of heat are incorporated in projection lens system PL1. Consequently, the stability of the performance of projection lens system PL1 can be improved, and the chromatic aberration can be successfully corrected.

3-3. Second Example

The measures for high brightness described above can be implemented not only in projection lens system PL1 of the first example but also in any projection lens system. Projection lens system PL2 of a second example will be described with reference to FIGS. 5 to 7.

FIG. 5 is a lens arrangement diagram in various states of projection lens system PL2 according to the second example. FIGS. 5(a), 5(b), 5(c) are lens arrangement diagrams at the wide-angle end, the intermediate position, and the telephoto end of projection lens system PL2, respectively, similarly to FIGS. 2(a) to 2(c).

Projection lens system PL2 of the second example includes 16 lens elements L1 to L16. In projection lens system PL2, first to sixteenth lens elements L1 to L16 are arranged in order from the magnification side to the reduction side, as in the first example. Projection lens system PL2 of the second example includes three lens groups G1 to G3 to constitute a zoom lens system, as in the first example. FIGS. 5(a) to 5(c) illustrate back glasses L17 to L19 as an example of transmission optical system 12.

In projection lens system PL2 of the second example, first lens group G1 includes first to sixth lens elements L1 to L6, and has a negative power. First lens element L1 has a negative meniscus shape, and its convex surface faces the magnification side. Second lens element L2 has a biconvex shape. Third lens element L3 has a negative meniscus shape, and its convex surface faces the magnification side. Fourth lens element L4 has a negative meniscus shape, and its convex surface faces the magnification side. Fifth lens element L5 has a biconcave shape. Sixth lens element L6 has a biconvex shape.

Second lens group G2 includes seventh and eighth lens elements L7, L8, and has a positive power. Seventh lens element L7 has a negative meniscus shape, and its convex surface faces the magnification side. Eighth lens element L8 has a biconvex shape. Seventh lens element L7 and eighth lens element L8 are bonded to each other.

Third lens group G3 includes ninth to sixteenth lens elements L9 to L16, and has a positive power. Diaphragm A is disposed on the magnification side of ninth lens element L9. Ninth lens element L9 has a biconcave shape. Tenth lens element L10 has a biconvex shape. Eleventh lens element L11 has a biconvex shape. Twelfth lens element L12 has a biconvex shape. Thirteenth lens element L13 has a biconcave shape. Fourteenth lens element L14 has a biconvex shape. Fifteenth lens element L15 has a negative meniscus shape, and its convex surface faces the reduction side. Sixteenth lens element L16 has a biconvex shape.

FIG. 6 is an aberration diagram illustrating longitudinal aberrations of projection lens system PL2 according to the second example. FIGS. 6(a), 6(b), 6(c) illustrate aberrations at the wide-angle end, the intermediate position, and the telephoto end of projection lens system PL2, respectively, similarly to FIGS. 3(a) to 3(c). The aberrations illustrated in FIGS. 6(a) to 6(c) are based on a second numerical example to be described later.

FIG. 7 illustrates sufficiency of conditions (1) to (11) in projection lens system PL2 according to the second example. The table illustrated in FIG. 7 shows a correspondence between each of conditions (1) to (11) and each of lens elements L1 to L16 in projection lens system PL2 of the second example, as in the first example. Projection lens system PL2 of the second embodiment can also improve the image quality of projection image 20 when the brightness of image projection device 1 is increased.

3-4. Third Example

Projection lens system PL3 of a third example will be described with reference to FIGS. 8 to 10.

FIG. 8 is a lens arrangement diagram in various states of projection lens system PL3 according to the third example. FIGS. 8(a), 8(b), 8(c) are lens arrangement diagrams at the wide-angle end, the intermediate position, and the telephoto end of projection lens system PL3, respectively, similarly to FIGS. 2(a) to 2(c).

Projection lens system PL3 of the third example includes 17 lens elements L1 to L17. In projection lens system PL3, first to seventeenth lens elements L1 to L17 are arranged in order from the magnification side to the reduction side, as in the first example. Projection lens system PL3 of the third example includes three lens groups G1 to G3 to constitute a zoom lens system, as in the first example. FIGS. 8(a) to 8(c) illustrate back glasses L18 to L20 as an example of transmission optical system 12.

In projection lens system PL3 of the third example, first lens group G1 includes first to sixth lens elements L1 to L6, and has a negative power. First lens element L1 has a negative meniscus shape, and its convex surface faces the magnification side. Second lens element L2 has a biconvex shape. Third lens element L3 has a negative meniscus shape, and its convex surface faces the magnification side. Fourth lens element L4 has a biconcave shape. Fifth lens element L5 has a biconcave shape. Sixth lens element L6 has a biconvex shape.

Second lens group G2 includes seventh to ninth lens elements L7 to L9, and has a positive power. Seventh lens element L7 has a positive meniscus shape, and its convex surface faces the magnification side. Eighth lens element L8 has a negative meniscus shape, and its convex surface faces the magnification side. Ninth lens element L9 has a biconvex shape.

Third lens group G3 includes tenth to seventeenth lens elements L10 to L17, and has a positive power. Diaphragm A is disposed on the magnification side of tenth lens element L10. Tenth lens element L10 has a biconcave shape. Eleventh lens element L11 has a biconvex shape. Twelfth lens element L12 has a biconvex shape. Thirteenth lens element L13 has a biconvex shape. Fourteenth lens element L14 has a biconcave shape. Fifteenth lens element L15 has a biconvex shape. Sixteenth lens element L16 has a negative meniscus shape, and its convex surface faces the reduction side. Seventeenth lens element L17 has a biconvex shape.

FIG. 9 is an aberration diagram illustrating longitudinal aberrations of projection lens system PL3 according to the third example. FIGS. 9(a), 9(b), 9(c) illustrate aberrations at the wide-angle end, the intermediate position, and the telephoto end of projection lens system PL3, respectively, similarly to FIGS. 3(a) to 3(c). The aberrations illustrated in FIGS. 9(a) to 9(c) are based on a third numerical example to be described later.

FIG. 10 illustrates sufficiency of conditions (1) to (11) in projection lens system PL3 according to the third example. The table illustrated in FIG. 10 shows a correspondence between each of conditions (1) to (11) and each of lens elements L1 to L17 in projection lens system PL3 of the third example, as in the first example. Projection lens system PL3 of the third example can also improve the image quality of projection image 20 when the brightness of image projection device 1 is increased.

3-5. About First to Third Examples

Projection lens systems PL1 to PL3 of the first to third examples described above can project image 2 on the reduction side in image projection device 1 to the magnification side as projection image 20. Projection lens systems PL1 to PL3 constitute a zoom lens system including diaphragm A and a plurality of lens groups G1 to G3. Lens group G1 closest to the magnification side in lens groups G1 to G3 has a negative power. Negative-lead projection lens systems PL1 to PL3 satisfy following condition (12) in the present exemplary embodiment.

Condition (12) is expressed by the following inequality. 2<fr/fw<4.5  (12)

Here, fr indicates the focal length at the wide-angle end on the reduction side of diaphragm A. Condition (12) defines above-described ratio fr/fw of focal length fr to focal length fw at the wide-angle end of a whole system.

Specifically, fr/fw=3.32 is satisfied in projection lens system PL1 of the first example. In projection lens system PL2 of the second example, fr/fw=3.73 is satisfied. In projection lens system PL3 of the third example, fr/fw=2.74 is satisfied.

According to condition (12), the performance of projection lens systems PL1 to PL3 constituting the negative-lead zoom lens system can be successfully achieved. If the ratio exceeds the upper limit value of condition (12), it becomes difficult to maintain the telecentricity on the reduction side while keeping a long back focus. If the ratio is less than the lower limit value of condition (12), it becomes difficult to correct the aberration, and the image quality of projection image 20 projected on the magnification side may be degraded. Ratio fr/fw is preferably larger than 2.5 and less than 4.0.

Second Exemplary Embodiment

A second exemplary embodiment will be described below with reference to the drawings. While the first exemplary embodiment has described an example in which projection lens system PL constitutes a zoom lens system, projection lens system PL is not limited to the zoom lens system. The second exemplary embodiment will describe projection lens system PL configured to form an intermediate image therein.

Hereinafter, description of configurations and operations similar to those of image projection device 1 and projection lens system PL according to the first exemplary embodiment will be appropriately omitted, and fourth to sixth examples will be described as examples of projection lens system PL according to the present exemplary embodiment.

1. Fourth Example

Projection lens system PL4 according to a fourth example of the present disclosure will be described with reference to FIGS. 11 to 14.

FIG. 11 is a lens arrangement diagram of projection lens system PL4 according to the fourth example. FIG. 12 is an aberration diagram illustrating longitudinal aberrations of projection lens system PL4 according to the fourth example. The aberration diagram of the present exemplary embodiment includes a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram in this order from the left side of the figure, as in the first exemplary embodiment. In the astigmatism diagram and the distortion aberration diagram according to the present exemplary embodiment, vertical axis “w” indicates a half angle of field.

FIGS. 11, 12 illustrate the arrangement of various lenses and various aberrations, respectively in a focused state where the projection distance of projection lens system PL4 according to the fourth example is 4,000 mm. A fourth numerical example corresponding to projection lens system PL4 of the fourth example will be described later.

As illustrated in FIG. 11, projection lens system PL4 of the fourth example includes 22 lens elements L1 to L22. In the present exemplary embodiment, first to twenty-second lens elements L1 to L22 in projection lens system PL4 are arranged in order from the magnification side to the reduction side, as in the first exemplary embodiment. Further, FIG. 11 also illustrates back glasses L23 to L25 as an example of transmission optical system 12.

In the present exemplary embodiment, first to twenty-second lens elements L1 to L22 in projection lens system PL4 constitute magnification optical system 51 and relay optical system 52. Magnification optical system 51 is located closer to the magnification side than relay optical system 52 is.

Magnification optical system 51 includes first to eleventh lens elements L1 to L11, and has a positive power. First lens element L1 has a negative meniscus shape, and its convex surface faces the magnification side. Second lens element L2 has a negative meniscus shape, and its convex surface faces the magnification side. Third lens element L3 has a negative meniscus shape, and its convex surface faces the magnification side.

Fourth lens element L4 has a biconvex shape. Fifth lens element L5 has a biconvex shape. Sixth lens element L6 has a biconcave shape. Fifth lens element L5 and sixth lens element L6 are bonded to each other. Seventh lens element L7 has a biconvex shape.

Eighth lens element L8 has a biconvex shape. Ninth lens element L9 has a biconcave shape. Eighth lens element L8 and ninth lens element L9 are bonded to each other. Tenth lens element L10 has a biconvex shape. Eleventh lens element L11 has a positive meniscus shape, and its convex surface faces the magnification side.

Relay optical system 52 includes twelfth to twenty-second lens elements L12 to L22, and has a positive power. Twelfth lens element L12 has a positive meniscus shape, and its convex surface faces the reduction side. Thirteenth lens element L13 has a biconcave shape. Twelfth lens element L12 and thirteenth lens element L13 are bonded to each other. Fourteenth lens element L14 has a positive meniscus shape, and its convex surface faces the reduction side. Fifteenth lens element L15 has a negative meniscus shape, and its convex surface faces the magnification side. Sixteenth lens element L16 has a biconvex shape. Diaphragm A is disposed between sixteenth lens element L16 and seventeenth lens element L17.

Seventeenth lens element L17 has a negative meniscus shape, and its convex surface faces the magnification side. Eighteenth lens element L18 has a biconvex shape. Nineteenth lens element L19 has a biconcave shape. Twentieth lens element L20 has a biconvex shape. Nineteenth lens element L19 and twentieth lens element L20 are bonded to each other. Twenty-first lens element L21 has a negative meniscus shape, and its convex surface faces the reduction side. Twenty-second lens element L22 has a biconvex shape.

FIG. 13 is an optical path diagram illustrating an optical path of a ray in projection lens system PL4 according to the fourth example. In the present exemplary embodiment, projection lens system PL4 includes intermediate imaging position MI between magnification optical system 51 and relay optical system 52. Projection lens system PL4 forms an image at intermediate imaging position MI that is conjugate with a reduction conjugate point on image plane S with relay optical system 52 on the reduction side interposed between intermediate imaging position MI and the reduction conjugate point. Further, imaging at intermediate imaging position MI of projection lens system PL4 is performed such that intermediate imaging position MI is conjugate with a magnification conjugate point located at a projection position of screen 4 or the like with magnification optical system 51 on the magnification side interposed between intermediate imaging position MI and the magnification conjugate point.

According to projection optical system PL4 of the present exemplary embodiment, as illustrated in FIG. 13, an angle between most off-axis principal ray 31 and axial ray 32 reaches near a right angle on the magnification side, and thus a wide angle of view of projection image 20 can be achieved.

FIG. 14 illustrates sufficiency of conditions (1) to (11) in projection lens system PL4 according to the fourth example. The table illustrated in FIG. 14 shows a correspondence between each of conditions (1) to (11) and each of lens elements L1 to L22 in projection lens system PL4 of the fourth example, as in the first exemplary embodiment. Projection lens system PL4 of the fourth example can also improve the image quality when the brightness is increased.

2. Fifth Example

Projection lens system PL5 of a fifth example will be described with reference to FIGS. 15 to 18.

FIG. 15 is a lens arrangement diagram of projection lens system PL5 according to the fifth example. FIG. 16 is an aberration diagram illustrating longitudinal aberrations of projection lens system PL5. FIGS. 15, 16 illustrate the arrangement of various lenses and various aberrations, respectively in a focused state where the projection distance of projection lens system PL5 according to the fifth example is 4,000 mm. A fifth numerical example corresponding to projection lens system PL5 of the fifth example will be described later.

FIG. 17 illustrates an optical path of a ray in projection lens system PL5 according to the fifth example. Projection lens system PL5 of the fifth example includes magnification optical system 51 closer to the magnification side than intermediate imaging position MI is, and relay optical system 52 closer to the reduction side than intermediate imaging position MI is, as in the fourth example.

In the fifth example, magnification optical system 51 includes first to eleventh lens elements L1 to L11, and has a positive power. First lens element L1 has a negative meniscus shape, and its convex surface faces the magnification side. Second lens element L2 has a negative meniscus shape, and its convex surface faces the magnification side. First lens element L1 and second lens element L2 are bonded to each other. Third lens element L3 has a negative meniscus shape, and its convex surface faces the magnification side.

Fourth lens element L4 has a positive meniscus shape, and its convex surface faces the reduction side. Fifth lens element L5 has a biconvex shape. Sixth lens element L6 has a biconcave shape. Fifth lens element L5 and sixth lens element L6 are bonded to each other. Seventh lens element L7 has a biconvex shape.

Eighth lens element L8 has a biconvex shape. Ninth lens element L9 has a biconcave shape. Eighth lens element L8 and ninth lens element L9 are bonded to each other. Tenth lens element L10 has a biconvex shape. Eleventh lens element L11 has a positive meniscus shape, and its convex surface faces the magnification side.

Relay optical system 52 includes twelfth to twenty-second lens elements L12 to L22, and has a positive power. Twelfth lens element L12 has a positive meniscus shape, and its convex surface faces the reduction side. Thirteenth lens element L13 has a biconcave shape. Twelfth lens element L12 and thirteenth lens element L13 are bonded to each other. Fourteenth lens element L14 has a biconvex shape. Fifteenth lens element L15 has a negative meniscus shape, and its convex surface faces the magnification side. Sixteenth lens element L16 has a biconvex shape. Diaphragm A is disposed between sixteenth lens element L16 and seventeenth lens element L17.

Seventeenth lens element L17 has a negative meniscus shape, and its convex surface faces the magnification side. Eighteenth lens element L18 has a biconvex shape. Nineteenth lens element L19 has a biconcave shape. Twentieth lens element L20 has a biconvex shape. Nineteenth lens element L19 and twentieth lens element L20 are bonded to each other. Twenty-first lens element L21 has a negative meniscus shape, and its convex surface faces the reduction side. Twenty-second lens element L22 has a biconvex shape.

FIG. 18 illustrates sufficiency of conditions (1) to (11) in projection lens system PL5 according to the fifth example. The table illustrated in FIG. 18 shows a correspondence between each of conditions (1) to (11) and each of lens elements L1 to L22 in projection lens system PL5 of the fifth example, as in the first exemplary embodiment. Projection lens system PL5 of the fifth example can also improve the image quality when the brightness is increased.

3. Sixth Example

Projection lens system PL6 of a sixth example will be described with reference to FIGS. 19 to 22.

FIG. 19 is a lens arrangement diagram of projection lens system PL6 according to the sixth example. FIG. 20 is an aberration diagram illustrating longitudinal aberrations of projection lens system PL6. FIGS. 19, 20 illustrate the arrangement of various lenses and various aberrations, respectively in a focused state where the projection distance of projection lens system PL6 according to the sixth example is 4,000 mm. A sixth numerical example corresponding to projection lens system PL6 of the sixth example will be described later.

FIG. 21 illustrates an optical path of a ray in projection lens system PL6 according to the sixth example. Projection lens system PL6 of the sixth example includes magnification optical system 51 closer to the magnification side than intermediate imaging position MI is, and relay optical system 52 closer to the reduction side than intermediate imaging position MI is, as in the fourth example.

In the sixth example, magnification optical system 51 includes first to eleventh lens elements L1 to L11, and has a positive power. First lens element L1 has a negative meniscus shape, and its convex surface faces the magnification side. Second lens element L2 has a negative meniscus shape, and its convex surface faces the magnification side. Third lens element L3 has a negative meniscus shape, and its convex surface faces the magnification side.

Fourth lens element L4 has a biconvex shape. Fifth lens element L5 has a positive meniscus shape, and its convex surface faces the reduction side. Sixth lens element L6 has a biconcave shape. Fifth lens element L5 and sixth lens element L6 are bonded to each other. Seventh lens element L7 has a biconvex shape.

Eighth lens element L8 has a biconvex shape. Ninth lens element L9 has a biconcave shape. Tenth lens element L10 has a biconvex shape. Eleventh lens element L11 has a positive meniscus shape, and its convex surface faces the magnification side.

Relay optical system 52 includes twelfth to twenty-second lens elements L12 to L22, and has a positive power. Twelfth lens element L12 has a positive meniscus shape, and its convex surface faces the reduction side. Thirteenth lens element L13 has a biconcave shape. Twelfth lens element L12 and thirteenth lens element L13 are bonded to each other. Fourteenth lens element L14 has a positive meniscus shape, and its convex surface faces the reduction side. Fifteenth lens element L15 has a negative meniscus shape, and its convex surface faces the magnification side. Sixteenth lens element L16 has a biconvex shape. Diaphragm A is disposed between sixteenth lens element L16 and seventeenth lens element L17.

Seventeenth lens element L17 has a negative meniscus shape, and its convex surface faces the magnification side. Eighteenth lens element L18 has a biconvex shape. Nineteenth lens element L19 has a biconcave shape. Twentieth lens element L20 has a biconvex shape. Nineteenth lens element L19, twentieth lens element L20, and twenty-first lens element L21 are bonded to each other. Twenty-first lens element L21 has a negative meniscus shape, and its convex surface faces the reduction side. Twenty-second lens element L22 has a biconvex shape.

FIG. 22 illustrates sufficiency of conditions (1) to (11) in projection lens system PL6 according to the sixth example. The table illustrated in FIG. 22 shows a correspondence between each of conditions (1) to (11) and each of lens elements L1 to L22 in projection lens system PL6 of the sixth example, as in the first exemplary embodiment. Projection lens system PL6 of the sixth example can also improve the image quality when the brightness is increased.

4. About Fourth to Sixth Examples

Projection lens systems PL4 to PL6 of the fourth to sixth examples described above include magnification optical system 51 and relay optical system 52 so as to have intermediate imaging position MI where imaging is performed inside the projection lens systems. In the present exemplary embodiment, projection lens systems PL4 to PL6 satisfy following condition (13).

Condition (13) is expressed by the following inequality. 8<|fr/f|<12  (13)

Here, fr indicates the focal length on the reduction side of diaphragm A. f indicates the focal length of the whole system.

Specifically, fr/f=10.09 is satisfied in projection lens system PL4 of the fourth example. In projection lens system PL5 of the fifth example, fr/f=9.17 is satisfied. In projection lens system PL6 of the sixth example, fr/f=10.25 is satisfied.

According to condition (13), the performance of projection lens systems PL4 to PL6 having intermediate imaging position MI can be successfully achieved. If the ratio exceeds the upper limit value of condition (13), it becomes difficult to maintain the telecentricity on the reduction side while keeping a long back focus. If the ratio is less than the lower limit value of condition (13), it becomes difficult to correct the aberration, and the image quality of projection image 20 may be degraded. Ratio fr/f is preferably larger than 8.5 and less than 11.

Third Exemplary Embodiment

A third exemplary embodiment will be described below with reference to the drawings. While the first exemplary embodiment has described an example in which projection lens system PL is of a negative-lead type, projection lens system PL may be of a positive-lead type. In the positive-lead type, the lens group closest to the magnification side in a zoom lens system has a positive power. The third exemplary embodiment will describe projection lens system PL that constitutes a positive-lead zoom lens system.

Hereinafter, description of configurations and operations similar to those of image projection device 1 and projection lens system PL according to the first exemplary embodiment will be appropriately omitted, and seventh to ninth examples will be described as examples of projection lens system PL according to the present exemplary embodiment.

1. Seventh Example

Projection lens system PL7 according to a seventh example of the present disclosure will be described with reference to FIGS. 23 to 25.

FIG. 23 is a lens arrangement diagram in various states of projection lens system PL7 according to the seventh example. FIGS. 23(a), 23(b), 23(c) are lens arrangement diagrams at the wide-angle end, the intermediate position, and the telephoto end of projection lens system PL7, respectively, similarly to FIGS. 2(a) to 2(c).

Projection lens system PL7 of the seventh example includes 16 lens elements L1 to L16 constituting five lens groups G1 to G5. As illustrated in FIG. 23(a), first to fifth lens groups G1 to G5 are arranged in order from the magnification side to the reduction side of projection lens system PL7. In the present exemplary embodiment, projection lens system PL7 functions as a zoom lens system by moving each of first to fifth lens groups G1 to G5 along an optical axis during zooming, as in the first exemplary embodiment.

In projection lens system PL7, first to sixteenth lens elements L1 to L16 are arranged in order from the magnification side to the reduction side, as in the first exemplary embodiment. FIGS. 23(a) to 23(c) illustrate back glasses L17 to L19 as an example of transmission optical system 12.

In the projection lens system PL7 of the seventh example, first lens group G1 includes first and second lens elements L1, L2, and has a positive power. First lens element L1 has a negative meniscus shape, and its convex surface faces the magnification side. Second lens element L2 has a biconvex shape.

Second lens group G2 includes third to fifth lens elements L3 to L5, and has a negative power. Third lens element L3 has a negative meniscus shape, and its convex surface faces the magnification side. Fourth lens element L4 has a negative meniscus shape, and its convex surface faces the magnification side. Fifth lens element L5 has a positive meniscus shape, and its convex surface faces the magnification side. Fourth lens element L4 and fifth lens element L5 are bonded to each other.

Third lens group G3 includes sixth lens element L6, and has a negative power. Sixth lens element L6 has a biconcave shape.

Fourth lens group G4 includes seventh to fourteenth lens elements L7 to L14, and has a positive power. Diaphragm A is disposed on the magnification side of seventh lens element L7. Seventh lens element L7 has a biconvex shape. Eighth lens element L8 has a negative meniscus shape, and its convex surface faces the reduction side. Ninth lens element L9 has a biconvex shape. Tenth lens element L10 has a biconvex shape. Eleventh lens element L11 has a biconcave shape. Twelfth lens element L12 has a biconvex shape. Thirteenth lens element L13 has a negative meniscus shape, and its convex surface faces the reduction side. Fourteenth lens element L14 has a biconvex shape.

Fifth lens group G5 includes fifteenth and sixteenth lens elements L15, L16, and has a positive power. Fifteenth lens element L15 has a negative meniscus shape, and its convex surface faces the magnification side. Sixteenth lens element L16 has a positive meniscus shape, and its convex surface faces the magnification side.

FIG. 24 is an aberration diagram illustrating longitudinal aberrations of projection lens system PL7 according to the seventh example. FIGS. 24(a), 24(b), 24(c) illustrate aberrations at the wide-angle end, the intermediate position, and the telephoto end of projection lens system PL7, respectively, similarly to FIGS. 3(a) to 3(c). The aberrations illustrated in FIGS. 24(a) to 24(c) are based on a seventh numerical example to be described later.

FIG. 25 illustrates sufficiency of conditions (1) to (11) in projection lens system PL7 according to the seventh example. The table illustrated in FIG. 25 shows a correspondence between each of conditions (1) to (11) and each of lens elements L1 to L16 in projection lens system PL7 of the seventh example, as in the first exemplary embodiment. Projection lens system PL7 of the seventh example can also improve the image quality when the brightness is increased.

2. Eighth Example

Projection lens system PL8 of an eighth example will be described with reference to FIGS. 26 to 28.

FIG. 26 is a lens arrangement diagram in various states of projection lens system PL8 according to the eighth example. FIGS. 26(a), 26(b), 26(c) are lens arrangement diagrams at the wide-angle end, the intermediate position, and the telephoto end of projection lens system PL8, respectively, similarly to FIGS. 2(a) to 2(c).

Projection lens system PL8 of the eighth example includes four lens groups G1 to G4 to constitute a zoom lens system, as in the seventh example. Projection lens system PL8 of the eighth example includes 17 lens elements L1 to L17. In projection lens system PL8, first to fourth lens groups G1 to G4 and first to seventeenth lens elements L1 to L17 are arranged in order from the magnification side to the reduction side, as in the seventh example. FIGS. 26(a) to 26(c) illustrate back glasses L18 to L20 as an example of transmission optical system 12.

In projection lens system PL8 of the eighth example, first lens group G1 includes first and second lens elements L1, L2, and has a positive power. First lens element L1 has a negative meniscus shape, and its convex surface faces the magnification side. Second lens element L2 has a biconvex shape.

Second lens group G2 includes third to sixth lens elements L3 to L6, and has negative power. Third lens element L3 has a negative meniscus shape, and its convex surface faces the magnification side. Fourth lens element L4 has a biconcave shape. Fifth lens element L5 has a biconcave shape. Sixth lens element L6 has a biconvex shape.

Third lens group G3 includes seventh to twelfth lens elements L7 to L12, and has a positive power. Seventh lens element L7 has a biconcave shape. Eighth lens element L8 has a biconvex shape. Diaphragm A is disposed between eighth lens element L8 and ninth lens element L9. Ninth lens element L9 has a negative meniscus shape, and its convex surface faces the reduction side. Tenth lens element L10 has a biconvex shape. Eleventh lens element L11 has a biconvex shape. Twelfth lens element L12 has a negative meniscus shape, and its convex surface faces the reduction side.

Fourth lens group G4 includes thirteenth to seventeenth lens elements L13 to L17, and has a positive power. Thirteenth lens element L13 has a biconvex shape. Fourteenth lens element L14 has a biconcave shape. Thirteenth lens element L13 and fourteenth lens element L14 are bonded to each other. Fifteenth lens element L15 has a biconvex shape. Sixteenth lens element L16 has a negative meniscus shape, and its convex surface faces the reduction side. Seventeenth lens element L17 has a biconvex shape.

FIG. 27 is an aberration diagram illustrating longitudinal aberrations of projection lens system PL8 according to the eighth example. FIGS. 27(a), 27(b), 27(c) illustrate aberrations at the wide-angle end, the intermediate position, and the telephoto end of projection lens system PL8, respectively, similarly to FIGS. 3(a) to 3(c). The aberrations illustrated in FIGS. 27(a) to 27(c) are based on an eighth numerical example to be described later.

FIG. 28 illustrates sufficiency of conditions (1) to (11) in projection lens system PL8 according to the eighth example. The table illustrated in FIG. 28 shows a correspondence between each of conditions (1) to (11) and each of lens elements L1 to L17 in projection lens system PL8 of the eighth example, as in the first exemplary embodiment. Projection lens system PL8 of the eighth example can also improve the image quality when the brightness is increased.

3. Ninth Example

Projection lens system PL9 of a ninth example will be described with reference to FIGS. 29 to 31.

FIG. 29 is a lens arrangement diagram in various states of the projection lens system PL9 according to the ninth example. FIGS. 29(a), 29(b), 29(c) are lens arrangement diagrams at the wide-angle end, the intermediate position, and the telephoto end of projection lens system PL9, respectively, similarly to FIGS. 2(a) to 2(c).

Projection lens system PL9 of the ninth example includes three lens groups G1 to G3 to constitute a zoom lens system, as in the seventh example. Projection lens system PL9 of the ninth example includes 19 lens elements L1 to L19. In projection lens system PL9, first to third lens groups G1 to G3 and first to nineteenth lens elements L1 to L19 are arranged in order from the magnification side to the reduction side, as in the seventh example. FIGS. 26(a) to 26(c) illustrate back glasses L20 to L22 as an example of transmission optical system 12.

In projection lens system PL9 of the ninth example, first lens group G1 includes first to fourth lens elements L1 to L4, and has a positive power. First lens element L1 has a biconvex shape. Second lens element L2 has a positive meniscus shape, and its convex surface faces the magnification side. Third lens element L3 has a biconcave shape. Fourth lens element L4 has a positive meniscus shape, and its convex surface faces the magnification side. Third lens element L3 and fourth lens element L4 are bonded to each other.

Second lens group G2 includes fifth to ninth lens elements L5 to L9, and has a negative power. Fifth lens element L5 has a positive meniscus shape, and its convex surface faces the magnification side. Sixth lens element L6 has a negative meniscus shape, and its convex surface faces the magnification side. Seventh lens element L7 has a biconcave shape. Eighth lens element L8 has a biconcave shape. Ninth lens element L9 has a positive meniscus shape, and its convex surface faces the magnification side.

Third lens group G3 includes tenth to nineteenth lens elements L10 to L19, and has a positive power. Diaphragm A is disposed on the magnification side of tenth lens element L10. Tenth lens element L10 has a biconvex shape. Eleventh lens element L11 has a negative meniscus shape, and its convex surface faces the reduction side. Twelfth lens element L12 has a biconvex shape. Thirteenth lens element L13 has a biconcave shape. Fourteenth lens element L14 has a biconvex shape. Thirteenth lens element L13 and fourteenth lens element L14 are bonded to each other.

Fifteenth lens element L15 has a negative meniscus shape, and its convex surface faces the magnification side. Sixteenth lens element L16 has a biconcave shape. Seventeenth lens element L17 has a positive meniscus shape, and its convex surface faces the reduction side. Eighteenth lens element L18 has a biconvex shape. Nineteenth lens element L19 has a biconvex shape.

FIG. 30 is an aberration diagram illustrating longitudinal aberrations of projection lens system PL9 according to the ninth example. FIGS. 30(a), 30(b), 30(c) illustrate aberrations at the wide-angle end, the intermediate position, and the telephoto end of projection lens system PL9, respectively, similarly to FIGS. 3(a) to 3(c). The aberrations illustrated in FIGS. 30(a) to 30(c) are based on a ninth numerical example to be described later.

FIG. 31 illustrates sufficiency of conditions (1) to (11) in projection lens system PL9 according to the ninth example. The table illustrated in FIG. 31 shows a correspondence between each of conditions (1) to (11) and each of lens elements L1 to L19 in projection lens system PL5 of the fifth example, as in the first exemplary embodiment. Projection lens system PL9 of the ninth example can also improve the image quality when the brightness is increased.

4. About Seventh to Ninth Examples

Projection lens systems PL7 to PL9 of the seventh to ninth examples described above constitute a positive-lead zoom lens system in which lens group G1 closest to the magnification side has a positive power. In the present exemplary embodiment, projection lens systems PL7 to PL9 satisfy following condition (14).

Condition (14) is expressed by the following inequality. 0.5<fr/ft<2.0  (14)

Here, fr indicates a combined focal length of all lenses closer to the reduction side than diaphragm A is in projection lens system PL9. Focal length fr is measured at the telephoto end, for example. Condition (14) defines above-described ratio fr/ft of focal length fr to focal length ft at the telephoto end of the whole system.

Specifically, fr/ft=0.83 is satisfied in projection lens system PL7 of the seventh example. In projection lens system PL8 of the eighth example, fr/ft=1.73 is satisfied. In projection lens system PL9 of the ninth example, fr/ft=0.63 is satisfied.

According to condition (14), the performance of projection lens systems PL7 to PL9 constituting the positive-lead zoom lens system can be successfully achieved. If the ratio exceeds the upper limit value of condition (14), it becomes difficult to maintain the telecentricity on the reduction side while keeping a long back focus. If the ratio is less than the lower limit value of condition (14), it becomes difficult to correct the aberration, and the image quality of projection image 20 may be degraded. Ratio fr/ft is preferably larger than 0.6 and less than 1.8.

NUMERICAL EXAMPLE

The first to ninth numerical examples for the first to ninth examples of projection lens systems PL1 to PL9 described above will be shown below.

1. First Numerical Example

The first numerical example corresponding to projection lens system PL1 of the first example will be shown below. In the first numerical example, Table 1-1 shows surface data, Table 1-2 shows various data, Table 1-3 shows single lens data, Table 1-4 shows zoom lens group data, and Table 1-5 shows zoom lens group magnification.

TABLE 1-1 EFFECTIVE SURFACE NUMBER r d nd vd DIAMETER OBJECT PLANE ∞ 1 107.78040 3.50000 1.80810 22.8 46.089 2 53.96420 12.67200 39.876 3 149.51330 8.08820 1.80518 25.5 39.759 4 −1854.88100 2.00000 39.150 5 165.88760 4.58880 1.80518 25.5 35.684 6 446.51990 0.20000 34.872 7 125.85010 2.80000 1.72916 54.7 32.582 8 45.71080 9.62350 28.318 9 586.50110 2.50000 1.49700 81.6 28.159 10 54.58600 14.05410 26.150 11 −52.66630 2.50000 1.49700 81.6 26.107 12 174.21610 10.48810 27.567 13 151.95810 16.84430 1.51680 64.2 30.780 14 −60.24780 22.13870 31.294 15 ∞ VARIABLE 26.292 16 73.49970 3.62090 1.49700 81.6 25.646 17 124.75200 5.38260 25.362 18 297.81230 2.20000 1.57501 41.5 24.746 19 72.75800 1.69030 24.048 20 101.16570 6.47700 1.49700 81.6 24.042 21 −172.31200 VARIABLE 23.873 (DIAPHRAGM) ∞ 2.75120 17.617 23 −69.97630 2.00000 1.48749 70.2 17.593 24 98.98570 2.38590 18.062 25 144.47980 3.69560 1.59270 35.4 18.479 26 −142.22100 21.27040 18.611 27 ∞ 30.00000 19.894 28 −9247.75800 5.22340 1.59270 35.4 26.066 29 −100.72470 7.09560 26.299 30 74.51100 9.57970 1.45860 90.2 27.108 31 −153.16810 1.03800 26.926 32 −220.70670 2.20000 1.83481 42.7 26.533 33 65.38850 2.74840 25.994 34 110.65610 10.66540 1.43700 95.1 26.130 35 −67.91250 1.25350 26.370 36 −60.12320 2.20000 1.73800 32.3 26.358 37 −128.20760 0.20000 27.358 38 90.61340 11.03110 1.45860 90.2 28.602 39 −98.83350 VARIABLE 28.681 40 ∞ 91.00000 1.51680 64.2 25.935 41 ∞ 1.00000 18.096 42 ∞ 1.00000 1.47401 65.4 17.964 43 ∞ 1.00000 17.876 44 ∞ 3.00000 1.50847 61.2 17.745 45 ∞ BF 17.485 IMAGE PLANE ∞

TABLE 1-2 ZOOM RATIO 1.36636 WIDE- INTER- TELE- ANGLE MEDIATE PHOTO FOCAL LENGTH 26.5860 30.9495 36.3260 F NUMBER 2.49940 2.50721 2.52404 ANGLE OF VIEW 33.9358 29.7135 25.7951 IMAGE HEIGHT 17.3500 17.3500 17.3500 LENS TOTAL LENGTH 447.4674 450.0141 433.1061 BF 1.00903 1.01425 1.00048 d15 84.2517 49.4763 3.0000 d21 2.0000 36.4577 60.0946 d39 16.5000 19.3592 25.3043 ENTRANCE PUPIL 65.3644 66.2582 66.0624 POSITION EXIT PUPIL −1557.2131 −1560.0723 −1566.0174 POSITION FRONT PRINCIPAL 91.4967 96.5941 101.5461 POINT POSITION REAR PRINCIPAL 420.7075 418.8290 396.4555 POINT POSITION

TABLE 1-3 LENS LENS FIRST SURFACE FOCAL LENGTH 1 1 −137.7465 2 3 172.1478 3 5 325.4375 4 7 −99.9195 5 9 −121.2919 6 11 −81.0738 7 13 85.8013 8 16 351.7199 9 18 −168.0414 10 20 129.2710 11 23 −83.7697 12 25 121.5047 13 28 171.7761 14 30 110.7689 15 32 −60.2146 16 34 98.0840 17 36 −155.5436 18 38 105.0032

TABLE 1-4 LENS LENS FIRST FOCAL CONFIGURATION FRONT PRINCIPAL REAR PRINCIPAL GROUP SURFACE LENGTH LENGTH POINT POSITION POINT POSITION 1 1 −93.98211 111.99770 −1.58474 −18.20875 2 16 216.18335 19.37080 6.75803 10.41823 3 22 88.39034 115.33820 83.41242 120.39718

TABLE 1-5 LENS FIRST WIDE- INTER- TELE- GROUP SURFACE ANGLE MEDIATE PHOTO 1 1 0.02297 0.02297 0.02297 2 16 −2.23199 −3.48227 −13.85352 3 22 0.12760 0.09519 0.02809

2. Second Numerical Example

The second numerical example corresponding to projection lens system PL2 of the second example will be shown below. In the second numerical example, Table 2-1 shows surface data, Table 2-2 shows various data, Table 2-3 shows single lens data, Table 2-4 shows zoom lens group data, and Table 2-5 shows zoom lens group magnification.

TABLE 2-1 EFFECTIVE SURFACE NUMBER r d nd vd DIAMETER OBJECT PLANE ∞ 1 110.83190 4.50000 1.80810 22.8 55.103 2 57.00040 15.67280 46.161 3 131.45310 11.61890 1.84666 23.8 46.043 4 −1168.12990 0.20000 45.278 5 99.66540 3.00000 1.72916 54.7 38.691 6 49.02990 12.54320 33.625 7 443.00480 2.80000 1.55032 75.5 33.447 8 58.98240 17.63270 30.708 9 −59.15460 2.50000 1.49700 81.6 30.665 10 128.27440 13.37030 32.714 11 171.14040 20.70470 1.48749 70.2 37.556 12 −60.67690 46.97390 38.031 13 ∞ VARIABLE 27.775 14 231.56720 2.20000 1.58144 40.7 25.511 15 82.57340 0.20000 25.016 16 81.63310 7.48880 1.49700 81.6 25.020 17 −196.19650 VARIABLE 24.827 (DIAPHRAGM) ∞ 2.48220 17.804 19 −80.83110 2.00000 1.48749 70.2 17.775 20 87.37540 2.38270 18.114 21 120.36880 3.61620 1.59270 35.4 18.493 22 −189.77620 30.22020 18.593 23 ∞ 29.99140 20.662 24 837.27770 5.67280 1.59270 35.4 27.395 25 −112.75940 7.18690 27.616 26 77.25820 10.13380 1.45860 90.2 28.402 27 −153.05450 1.02370 28.213 28 −213.74150 2.20000 1.83481 42.7 27.800 29 65.32170 2.53740 27.215 30 98.17320 11.68970 1.43700 95.1 27.365 31 −71.59400 1.56330 27.613 32 −60.95470 2.20000 1.73800 32.3 27.602 33 −130.98280 0.20000 28.708 34 99.88370 11.85120 1.45860 90.2 30.071 35 −92.55720 VARIABLE 30.161 36 ∞ 91.00000 1.51680 64.2 26.589 37 ∞ 1.00000 18.151 38 ∞ 1.00000 1.47401 65.4 18.010 39 ∞ 1.00000 17.914 40 ∞ 3.00000 1.50847 61.2 17.773 41 ∞ BF 17.498 IMAGE PLANE ∞

TABLE 2-2 ZOOM RATIO 1.32931 WIDE- INTER- TELE- ANGLE MEDIATE PHOTO FOCAL LENGTH 23.6871 27.2973 31.4874 F NUMBER 2.49959 2.50085 2.50838 ANGLE OF VIEW 37.0162 32.8897 29.1191 IMAGE HEIGHT 17.3500 17.3500 17.3500 LENS TOTAL LENGTH 499.8013 500.0092 482.8781 BF 1.00131 1.00920 1.00238 d13 94.8321 58.1504 12.0921 d17 2.0000 37.1341 62.4686 d35 16.6111 18.3587 21.9582 ENTRANCE PUPIL 71.4309 71.8383 71.5044 POSITION EXIT PUPIL 3335.5562 3333.8086 3330.2091 POSITION FRONT PRINCIPAL 95.2862 99.3592 103.2895 POINT POSITION REAR PRINCIPAL 475.9765 472.5289 451.1472 POINT POSITION

TABLE 2-3 LENS LENS FIRST SURFACE FOCAL LENGTH 1 1 −150.8621 2 3 140.1299 3 5 −135.7424 4 7 −123.9602 5 9 −81.0996 6 11 94.6600 7 14 −221.9264 8 16 117.0386 9 19 −85.7966 10 21 124.8079 11 24 168.0392 12 26 113.5250 13 28 −59.7174 14 30 96.7663 15 32 −156.5760 16 34 106.8237

TABLE 2-4 LENS LENS FIRST FOCAL CONFIGURATION FRONT PRINCIPAL REAR PRINCIPAL GROUP SURFACE LENGTH LENGTH POINT POSITION POINT POSITION 1 1 −102.80219 151.51650 −4.42699 −34.35141 2 14 245.51015 9.88880 4.07852 7.32867 3 18 88.38252 126.95150 90.73331 132.48997

TABLE 2-5 LENS FIRST WIDE- INTER- TELE- GROUP SURFACE ANGLE MEDIATE PHOTO 1 1 0.02508 0.02508 0.02508 2 14 −1.76003 −2.38799 −4.32602 3 18 0.13178 0.11191 0.07126

3. Third Numerical Example

The third numerical example corresponding to projection lens system PL3 of the third example will be shown below. In the third numerical example, Table 3-1 shows surface data, Table 3-2 shows various data, Table 3-3 shows single lens data, Table 3-4 shows zoom lens group data, and Table 3-5 shows zoom lens group magnification.

TABLE 3-1 EFFECTIVE SURFACE NUMBER r d nd vd DIAMETER OBJECT PLANE ∞ 1 92.39910 3.50000 1.80518 25.5 40.533 2 49.78520 8.95250 35.661 3 99.58080 10.50950 1.73800 32.3 35.558 4 −423.52170 0.20000 34.840 5 130.71780 2.80000 1.48749 70.2 31.291 6 46.53950 10.47680 27.334 7 −326.42190 2.50000 1.49700 81.6 27.142 8 57.90150 12.80740 25.026 9 −50.19340 2.50000 1.49700 81.6 24.976 10 140.39530 8.49020 26.342 11 147.86110 14.35050 1.59349 67.0 28.868 12 −63.20500 15.76340 29.277 13 ∞ VARIABLE 25.472 14 52.41280 2.79250 1.49700 81.6 23.984 15 64.38550 4.61480 23.651 16 155.59380 2.20000 1.56732 42.8 23.383 17 55.82770 1.57090 22.620 18 69.35150 7.11910 1.49700 81.6 22.630 19 −190.60620 VARIABLE 22.425 (DIAPHRAGM) ∞ 2.74710 17.158 21 −66.54020 2.00000 1.48749 70.2 17.134 22 98.09230 2.82800 17.560 23 234.45100 3.54150 1.59270 35.4 17.971 24 −146.72000 12.07980 18.164 25 ∞ 28.96150 19.328 26 1899.45620 5.81140 1.59270 35.4 25.811 27 −90.88760 15.96040 26.052 28 69.48980 9.95460 1.45860 90.2 27.032 29 −154.02640 0.91520 26.810 30 −240.90810 2.20000 1.83481 42.7 26.369 31 63.18500 3.41010 25.665 32 132.89910 10.23150 1.43700 95.1 25.786 33 −63.96890 1.01590 26.014 34 −58.89590 2.20000 1.73800 32.3 25.993 35 −125.64590 0.20000 26.952 36 86.69430 11.00180 1.45860 90.2 28.091 37 −97.34420 VARIABLE 28.176 38 ∞ 91.00000 1.51680 64.2 25.566 39 ∞ 1.00000 18.066 40 ∞ 1.00000 1.47401 65.4 17.940 41 ∞ 1.00000 17.856 42 ∞ 3.00000 1.50847 61.2 17.730 43 ∞ BF 17.481 IMAGE PLANE ∞

TABLE 3-2 ZOOM RATIO 1.37093 WIDE- INTER- TELE- ANGLE MEDIATE PHOTO FOCAL LENGTH 31.4881 36.8327 43.1680 F NUMBER 2.49951 2.50704 2.52632 ANGLE OF VIEW 29.6093 25.6352 22.1374 IMAGE HEIGHT 17.3500 17.3500 17.3500 LENS TOTAL LENGTH 419.8112 420.0168 406.2001 BF 1.01081 1.01648 0.99737 d13 77.0940 44.3060 3.0000 d19 2.0000 32.3714 54.4914 d37 16.5000 19.1165 24.5049 ENTRANCE PUPIL 66.7945 67.6839 67.6248 POSITION EXIT PUPIL −1374.6242 −1377.2407 −1382.6291 POSITION FRONT PRINCIPAL 97.5617 103.5320 109.4455 POINT POSITION REAR PRINCIPAL 388.0793 382.8505 362.5738 POINT POSITION

TABLE 3-3 LENS LENS FIRST SURFACE FOCAL LENGTH 1 1 −139.1657 2 3 110.1867 3 5 −149.8825 4 7 −98.7373 5 9 −74.0732 6 11 76.5439 7 14 526.3668 8 16 −154.7070 9 18 103.2530 10 21 −81.0051 11 23 152.7878 12 26 146.5011 13 28 105.9011 14 30 −59.7646 15 32 100.4043 16 34 −152.3515 17 36 101.9063

TABLE 3-4 LENS LENS FIRST FOCAL CONFIGURATION FRONT PRINCIPAL REAR PRINCIPAL GROUP SURFACE LENGTH LENGTH POINT POSITION POINT POSITION 1 1 −109.90907 92.85030 −4.61772 −16.76671 2 14 195.72199 18.29730 6.90200 10.53971 3 20 86.26237 115.05880 80.90515 124.33705

TABLE 3-5 LENS FIRST WIDE- INTER- TELE- GROUP SURFACE ANGLE MEDIATE PHOTO 1 1 0.02677 0.02677 0.02677 2 14 −1.86655 −2.71574 −6.36214 3 20 0.15497 0.12457 0.06233

4. Fourth Numerical Example

The fourth numerical example corresponding to projection lens system PL4 of the fourth example will be shown below. In the fourth numerical example, Table 4-1 shows surface data, Table 4-2 shows various data, and Table 4-3 shows single lens data.

TABLE 4-1 EFFECTIVE SURFACE NUMBER r d nd vd DIAMETER OBJECT PLANE 4200.00000 1 58.29070 3.50000 1.90366 31.3 35.030 2 30.46270 9.87360 25.206 3 74.23120 2.50000 1.80420 46.5 23.970 4 20.18290 4.02130 16.791 5 27.53570 2.00000 1.59349 67.0 16.464 6 16.59290 33.03140 13.787 7 1306.65610 2.50000 1.49700 81.6 7.770 8 −33.58300 5.21580 8.270 9 163.20330 5.00000 1.49700 81.6 11.098 10 −24.49910 0.87720 11.533 11 −25.37780 2.00000 1.59270 35.4 11.644 12 58.39790 3.39920 13.302 13 283.07260 6.69100 1.49700 81.6 14.881 14 −29.85650 24.49410 15.620 15 60.11530 13.61550 1.49700 81.6 25.697 16 −60.11530 0.36560 25.732 17 −72.47510 2.50000 1.64769 33.8 25.377 18 53.43880 7.97450 25.622 19 251.51420 9.56110 1.80809 22.8 27.033 20 −67.48230 2.10320 27.471 21 54.36810 10.00000 1.80809 22.8 27.449 22 456.19300 25.13310 26.607 23 −95.96650 5.00000 1.48749 70.4 18.010 24 −40.63500 0.29540 17.849 25 −47.89710 2.00000 1.72825 28.3 17.400 26 47.89710 64.25370 17.143 27 −1901.14330 11.00000 1.67300 38.3 31.991 28 −70.97520 87.25490 32.501 29 129.52100 2.20000 1.48749 70.4 23.923 30 69.35160 6.47060 23.437 31 106.68220 6.00000 1.59270 35.4 23.561 32 −404.62060 59.14870 23.383 (DIAPHRAGM) ∞ 62.62650 18.621 34 137.59820 2.20000 1.73800 32.3 21.734 35 67.94860 3.50290 21.716 36 107.89620 9.26120 1.45860 90.2 22.307 37 −53.81450 0.20000 22.513 38 −80.61170 2.20000 1.73800 32.3 22.398 39 80.61170 0.40000 23.217 40 90.38150 11.26690 1.45860 90.2 23.226 41 −47.74290 2.50960 23.617 42 −44.25950 2.20000 1.73800 32.3 23.686 43 −67.28880 0.20000 24.879 44 73.08750 8.00000 1.80420 46.5 26.811 45 −1277.58600 16.38070 26.621 46 ∞ 91.00000 1.51680 64.2 24.137 47 ∞ 1.00000 15.245 48 ∞ 1.00000 1.47401 65.4 15.096 49 ∞ 1.00000 14.996 50 ∞ 3.00000 1.50847 61.2 14.847 51 ∞ BF 14.552 IMAGE PLANE ∞

TABLE 4-2 FOCAL LENGTH −9.0016 F NUMBER 2.49133 ANGLE OF VIEW 91.6000 IMAGE HEIGHT 14.4018 LENS TOTAL LENGTH 638.9384 BF 1.01074 ENTRANCE PUPIL POSITION 22.8656 EXIT PUPIL POSITION 4741.8979 FRONT PRINCIPAL 13.8810 POINT POSITION REAR PRINCIPAL 647.9199 POINT POSITION

TABLE 4-3 LENS LENS FIRST SURFACE FOCAL LENGTH 1 1 −75.0960 2 3 −35.1943 3 5 −75.4904 4 7 65.9194 5 9 43.2427 6 11 −29.5838 7 13 54.7307 8 15 62.8411 9 17 −47.1225 10 19 66.7366 11 21 75.5428 12 23 140.4130 13 25 −32.5983 14 27 109.2865 15 29 −309.9497 16 31 143.0623 17 34 −184.3668 18 36 79.7309 19 38 −54.3003 20 40 69.9150 21 42 −182.6403 22 44 86.1922

5. Fifth Numerical Example

The fifth numerical example corresponding to projection lens system PL5 of the fifth example will be shown below. In the fifth numerical example, Table 5-1 shows surface data, Table 5-2 shows various data, and Table 5-3 shows single lens data.

TABLE 5-1 EFFECTIVE SURFACE NUMBER r d nd vd DIAMETER OBJECT PLANE 4050.00000 1 62.54190 4.00000 1.90366 31.3 40.025 2 43.40300 0.20000 32.241 3 43.42470 3.00000 1.92286 20.9 32.095 4 28.60770 13.44750 25.019 5 142.04020 2.50000 1.59349 67.0 23.536 6 16.66020 40.19710 14.978 7 −190.87630 5.00000 1.49700 81.6 13.637 8 −29.87760 0.20000 14.435 9 119.72050 9.48830 1.49700 81.6 16.581 10 −36.90040 0.38640 17.429 11 −42.06130 2.00000 1.59270 35.4 17.491 12 55.78560 4.07030 19.405 13 113.80070 9.77420 1.49700 81.6 21.393 14 −43.52370 19.40830 22.003 15 64.10310 16.14710 1.49700 81.6 29.629 16 −64.10310 0.20000 29.579 17 −74.12660 2.50000 1.64769 33.8 29.049 18 59.00950 14.50800 28.735 19 162.73460 11.09220 1.80809 22.8 32.836 20 −96.55920 0.20000 33.037 21 51.05620 10.24630 1.80809 22.8 31.284 22 190.75090 24.49070 30.524 23 −71.77370 5.00000 1.48749 70.4 20.550 24 −46.98370 0.26930 20.221 25 −54.82480 2.00000 1.72825 28.3 19.681 26 54.82480 78.98270 19.151 27 5260.54060 11.00000 1.67300 38.3 32.662 28 −82.97150 60.14730 33.065 29 129.08740 2.20000 1.48749 70.4 26.056 30 64.33920 10.00000 25.510 31 96.61770 7.00000 1.59270 35.4 25.640 32 −747.95790 55.00000 25.522 (DIAPHRAGM) ∞ 56.88490 18.198 34 131.50790 2.20000 1.73800 32.3 23.251 35 65.30700 3.71530 23.275 36 100.52430 10.61220 1.45860 90.2 23.955 37 −53.31120 0.20000 24.168 38 −78.15180 2.20000 1.73800 32.3 24.015 39 78.15180 1.01200 24.990 40 90.63280 13.05900 1.45860 90.2 25.239 41 −47.23820 0.86090 25.634 42 −45.46180 2.20000 1.73800 32.3 25.642 43 −68.28750 0.20000 26.948 44 74.30690 8.00000 1.80420 46.5 29.112 45 −1234.88000 16.20000 29.038 46 ∞ 91.00000 1.51680 64.2 26.257 47 ∞ 1.00000 16.248 48 ∞ 1.00000 1.47401 65.4 16.080 49 ∞ 1.00000 15.967 50 ∞ 3.00000 1.50847 61.2 15.799 51 ∞ BF 15.467 IMAGE PLANE ∞

TABLE 5-2 FOCAL LENGTH −9.7020 F NUMBER 2.49196 ANGLE OF VIEW 90.1000 IMAGE HEIGHT 15.2985 LENS TOTAL LENGTH 640.0155 BF 1.01555 ENTRANCE PUPIL POSITION 26.5328 EXIT PUPIL POSITION 11473.0231 FRONT PRINCIPAL 16.8390 POINT POSITION REAR PRINCIPAL 649.6942 POINT POSITION

TABLE 5-3 LENS LENS FIRST SURFACE FOCAL LENGTH 1 1 −174.2394 2 3 −100.6282 3 5 −32.0394 4 7 70.5450 5 9 57.9188 6 11 −40.1541 7 13 64.6803 8 15 67.3046 9 17 −50.3546 10 19 76.4550 11 21 83.5348 12 23 261.7415 13 25 −37.3544 14 27 121.4723 15 29 −266.0907 16 31 144.8104 17 34 −178.3050 18 36 77.6470 19 38 −52.6338 20 40 69.7918 21 42 −192.1567 22 44 87.3924

6. Sixth Numerical Example

The sixth numerical example corresponding to projection lens system PL6 of the sixth example will be shown below. In the sixth numerical example, Table 6-1 shows surface data, Table 6-2 shows various data, and Table 6-3 shows single lens data.

TABLE 6-1 EFFECTIVE SURFACE NUMBER r d nd vd DIAMETER OBJECT PLANE 5200.00000 1 62.46790 4.00000 1.90366 31.3 40.036 2 35.50310 9.99990 29.032 3 65.29260 2.50000 1.72916 54.7 26.366 4 21.11420 4.58070 17.761 5 29.11320 2.00000 1.62041 60.3 17.189 6 13.41680 19.55940 12.485 7 197.68480 15.00000 1.49700 81.6 7.059 8 −26.28950 0.20000 10.171 9 −2228.75270 5.57310 1.49700 81.6 11.148 10 −20.02520 0.86840 11.669 11 −20.56810 2.00000 1.59270 35.4 11.750 12 57.19250 3.98030 13.975 13 433.88500 8.40840 1.49700 81.6 16.439 14 −27.36790 19.51560 17.377 15 65.80080 15.52120 1.49700 81.6 29.255 16 −65.80080 0.20000 29.334 17 −94.65310 2.50000 1.64769 33.8 28.832 18 55.58010 7.96650 29.048 19 276.62580 10.51270 1.80809 22.8 29.858 20 −69.45390 0.20000 30.305 21 56.40440 11.00000 1.80809 22.8 30.906 22 520.65430 28.51500 30.215 23 −94.14750 5.00000 1.48749 70.4 20.820 24 −41.68990 0.20000 20.700 25 −50.81930 2.00000 1.72825 28.3 19.921 26 50.81930 72.03570 19.466 27 −26168.82480 10.79210 1.67300 38.3 35.835 28 −78.20080 81.49680 36.073 29 123.44890 2.20000 1.48749 70.2 27.688 30 67.17520 10.00000 27.134 31 106.41330 6.00000 1.59270 35.4 27.223 32 −496.67740 60.00000 27.195 (DIAPHRAGM) ∞ 57.73490 18.222 34 143.68540 2.20000 1.73800 32.3 22.851 35 65.87630 3.68330 22.854 36 103.15140 10.29040 1.45860 90.2 23.481 37 −52.61520 0.20000 23.690 38 −78.63750 2.20000 1.73800 32.3 23.558 39 78.63750 1.07720 24.517 40 93.52620 12.68120 1.45860 90.2 24.762 41 −46.50510 1.00730 25.168 42 −44.03590 2.20000 1.73800 32.3 25.179 43 −68.57950 0.20000 26.570 44 79.77200 8.00000 1.80420 46.5 28.745 45 −376.98300 16.20000 28.696 46 ∞ 91.00000 1.51680 64.2 25.888 47 ∞ 1.00000 16.217 48 ∞ 1.00000 1.47401 65.4 16.055 49 ∞ 1.00000 15.945 50 ∞ 3.00000 1.50847 61.2 15.783 51 ∞ BF 15.462 IMAGE PLANE ∞

TABLE 6-2 FOCAL LENGTH −8.6519 F NUMBER 2.49176 ANGLE OF VIEW 102.0000 IMAGE HEIGHT 15.2911 LENS TOTAL LENGTH 640.0172 BF 1.01709 ENTRANCE PUPIL POSITION 23.9896 EXIT PUPIL POSITION 3190.3911 FRONT PRINCIPAL 15.3612 POINT POSITION REAR PRINCIPAL 648.6505 POINT POSITION

TABLE 6-3 LENS LENS FIRST SURFACE FOCAL LENGTH 1 1 −97.9115 2 3 −43.8424 3 5 −42.1679 4 7 47.7495 5 9 40.6236 6 11 −25.2813 7 13 52.1146 8 15 68.8960 9 17 −53.7142 10 19 69.6451 11 21 77.4598 12 23 148.8358 13 25 −34.6045 14 27 116.5262 15 29 −306.2142 16 31 148.4094 17 34 −166.8402 18 36 77.5883 19 38 −52.9629 20 40 69.7144 21 42 −173.3243 22 44 82.5144

7. Seventh Numerical Example

The seventh numerical example corresponding to projection lens system PL7 of the seventh example will be shown below. In the seventh numerical example, Table 7-1 shows surface data, Table 7-2 shows various data, Table 7-3 shows single lens data, Table 7-4 shows zoom lens group data, and Table 7-5 shows zoom lens group magnification.

TABLE 7-1 EFFEC- TIVE SURFACE DIAM- NUMBER r d nd vd ETER OBJECT PLANE ∞  1 119.63260 3.60000 1.73800 32.3 46.981  2 82.63570 1.37420 44.342  3 82.10820 17.54780 1.48749 70.2 44.063  4 −492.95470 VARIABLE 43.313  5 396.98350 3.00000 1.45860 90.2 39.404  6 52.75470 11.52230 33.669  7 498.51150 2.30000 1.43700 95.1 33.525  8 48.67720 0.20000 30.904  9 48.59130 8.09800 1.83481 42.7 30.911 10 97.69030 VARIABLE 30.325 11 −62.41280 2.00000 1.51680 64.2 16.452 12 155.69540 VARIABLE 15.888 (DIAPHRAGM) ∞ 14.27120 17.573 14 226.47090 5.55080 1.49700 81.6 20.448 15 −94.70770 2.71950 20.667 16 −49.75820 2.00000 1.51680 64.2 20.682 17 −489.23030 16.10820 21.714 18 1212.41950 8.56290 1.55032 75.5 25.755 19 −61.90930 0.20000 26.127 20 99.12130 6.02390 1.59270 35.4 25.862 21 −448.62530 10.51210 25.748 22 −129.19760 2.00000 1.67300 38.3 24.585 23 88.98480 2.01880 24.777 24 156.03790 7.45720 1.43700 95.1 24.903 25 −92.95600 2.93710 25.160 26 −56.61360 2.20000 1.67300 38.3 25.186 27 −75.37180 29.79590 25.969 28 139.38740 10.39010 1.43700 95.1 30.966 29 −107.37960 VARIABLE 31.014 30 72.00060 2.20000 1.73800 32.3 28.559 31 52.17770 3.45230 27.535 32 79.83990 5.93100 1.43700 95.1 27.541 33 485.77180 VARIABLE 27.355 34 ∞ 91.00000 1.51680 64.2 35.000 35 ∞ 1.00000 35.000 36 ∞ 1.00000 1.47401 65.4 35.000 37 ∞ 1.00000 35.000 38 ∞ 3.00000 1.50847 61.2 35.000 39 ∞ BF 35.000 IMAGE PLANE ∞

TABLE 7-2 ZOOM RATIO 2.09537 WIDE-ANGLE INTERMEDIATE TELEPHOTO FOCAL LENGTH 49.5209 71.7754 103.7644 F NUMBER 2.50418 2.52428 2.55044 ANGLE OF VIEW 19.4618 13.5353 9.4178 IMAGE HEIGHT 17.3500 17.3500 17.3500 LENS TOTAL 400.0363 400.0371 400.0365 LENGTH BF 1.03636 1.03736 1.03674 d4 2.0000 31.0606 55.5593 d10 48.0327 25.8580 6.0000 d12 49.4939 33.4964 16.7471 d29 2.0000 8.9573 20.0494 d33 16.5000 18.6541 19.6707 ENTRANCE 116.3070 155.9682 177.4489 PUPIL POSITION EXIT PUPIL −2340.4497 −2404.5080 −2509.0183 POSITION FRONT 164.7803 225.6008 276.9193 PRINCIPAL POINT POSITION REAR PRINCIPAL 349.9194 327.0215 293.6921 POINT POSITION

TABLE 7-3 LENS FIRST FOCAL LENS SURFACE LENGTH 1 1 −377.6776 2 3 145.8403 3 5 −133.0292 4 7 −123.6350 5 9 107.7270 6 11 −85.9412 7 14 135.1438 8 16 −107.3494 9 18 107.2869 10 20 137.5355 11 22 −78.0076 12 24 134.5272 13 26 −354.7417 14 28 140.5959 15 30 −269.5021 16 32 217.6663

TABLE 7-4 LENS LENS FRONT REAR FIRST CONFIG- PRINCIPAL PRINCIPAL SUR- FOCAL URATION POINT POINT GROUP FACE LENGTH LENGTH POSITION POSITION 1 1 239.39037  22.52200  4.11345 11.19786 2 5 −146.61717  25.12030  6.17551 12.34573 3 11 −85.94124   2.00000  0.37614  1.06168 4 13 87.46411 122.74770 77.80724 68.40232 5 30 1150.60590  11.58330  0.31837  3.02611

TABLE 7-5 LENS FIRST WIDE- GROUP SURFACE ANGLE INTERMEDIATE TELEPHOTO 1 1 −0.06359 −0.06359 −0.06359 2 5 −1.65677 −2.46684 −4.19667 3 11 0.16014 0.13572 0.09912 4 13 −0.77434 −0.88298 −1.02356 5 30 0.92112 0.91925 0.91837

8. Eighth Numerical Example

The eighth numerical example corresponding to projection lens system PL8 of the eighth example will be shown below. In the eighth numerical example, Table 8-1 shows surface data, Table 8-2 shows various data, Table 8-3 shows single lens data, Table 8-4 shows zoom lens group data, and Table 8-5 shows zoom lens group magnification.

TABLE 8-1 EFFEC- TIVE SURFACE DIAM- NUMBER r d nd vd ETER OBJECT PLANE ∞  1 140.86220  3.50000 1.80518 25.5 50.098  2 70.77190  6.65020 45.723  3 72.95750 18.75130 1.71300 53.9 45.230  4 −3623.56460 VARIABLE 44.155  5 99.41190  2.80000 1.62041 60.3 34.111  6 48.47160 12.35230 29.676  7 −248.16440  2.20000 1.49700 81.6 29.418  8 40.54330 11.62120 25.559  9 −156.72080  2.20000 1.49700 81.6 25.527 10 121.32590  0.20000 25.546 11 60.41060  9.57380 1.53172 48.8 25.995 12 −211.50600 VARIABLE 25.775 13 −369.79680  2.00000 1.51680 64.2 16.956 14 66.72950 21.51370 16.863 15 140.00500  4.47440 1.73800 32.3 19.319 16 −207.41910 31.79060 19.341 (DIAPHRAGM) ∞ 35.45230 17.653 18 −40.60280  2.00000 1.51680 64.2 19.262 19 −87.84240  0.20000 20.227 20 61053.92850  6.91030 1.45860 90.2 20.739 21 −47.38380 15.98190 21.009 22 565.18380  6.20960 1.45860 90.2 23.518 23 −75.02470  2.04150 23.664 24 −54.73590  2.20000 1.62041 60.3 23.672 25 −81.29720 VARIABLE 24.279 26 132.45390  6.38890 1.45860 90.2 25.636 27 −162.62640  0.87130 25.599 28 −137.17440  2.20000 1.56732 42.8 25.547 29 65.21460  4.13410 25.581 30 210.03830  6.67350 1.45860 90.2 25.713 31 −107.32330  3.75380 25.980 32 −55.69280  2.20000 1.57501 41.5 26.025 33 −87.38950  0.20000 27.087 34 108.80930 11.73560 1.45860 90.2 28.715 35 −76.22200 VARIABLE 28.843 36 ∞ 91.00000 1.51680 64.2 35.000 37 ∞  1.00000 35.000 38 ∞  1.00000 1.47401 65.4 35.000 39 ∞  1.00000 35.000 40 ∞  3.00000 1.50847 61.2 35.000 41 ∞ BF 35.000 IMAGE PLANE ∞

TABLE 8-2 ZOOM RATIO 1.51231 WIDE-ANGLE INTERMEDIATE TELEPHOTO FOCAL LENGTH 34.1871 41.9922 51.7016 F NUMBER 2.43804 2.48215 2.54999 ANGLE OF VIEW 27.0946 22.3213 18.3988 IMAGE HEIGHT 17.3500 17.3500 17.3500 LENS TOTAL 400.0069 400.0112 400.0169 LENGTH BF 1.00697 1.01140 1.01699 d4 2.0000 15.5123 25.9815 d12 42.7196 22.4145 2.0000 d25 2.0000 7.5016 16.0149 d35 16.5000 17.7911 19.2232 ENTRANCE 86.2320 106.7704 121.5252 PUPIL POSITION EXIT PUPIL −3123.3315 −20579.1398 2644.3686 POSITION FRONT 120.0451 148.6944 174.2378 PRINCIPAL POINT POSITION REAR PRINCIPAL 365.6277 357.7302 347.8787 POINT POSITION

TABLE 8-3 LENS FIRST FOCAL LENS SURFACE LENGTH 1 1 −180.6701 2 3 100.5174 3 5 −155.7483 4 7 −69.9437 5 9 −137.2363 6 11 89.4665 7 13 −109.2124 8 15 113.8826 9 18 −148.2324 10 20 103.2469 11 22 144.8664 12 24 −278.8791 13 26 160.2695 14 28 −77.6061 15 30 155.9150 16 32 −273.9798 17 34 99.7282

TABLE 8-4 LENS LENS FRONT REAR FIRST CONFIG- PRINCIPAL PRINCIPAL SUR- FOCAL URATION POINT POINT GROUP FACE LENGTH LENGTH POSITION POSITION 1 1 213.60964  28.90150 14.32267  23.89963 2 5 −63.46879  40.94730  5.49345  9.13155 3 13 115.89625 130.77430 98.38591 133.13053 4 26 141.40701  38.15720 32.06527  42.14905

TABLE 8-5 LENS FIRST WIDE- GROUP SURFACE ANGLE INTERMEDIATE TELEPHOTO 1 1 −0.03682 −0.03682 −0.03682 2 5 −0.43618 −0.48083 −0.52225 3 13 −0.78215 −0.88669 −1.02635 4 26  0.44715 0.43799  0.42782

9. Ninth Numerical Example

The ninth numerical example corresponding to projection lens system PL9 of the ninth example will be shown below. In the ninth numerical example, Table 9-1 shows surface data, Table 9-2 shows various data, Table 9-3 shows single lens data, Table 9-4 shows zoom lens group data, and Table 9-5 shows zoom lens group magnification.

TABLE 9-1 EFFEC- TIVE SURFACE DIAM- NUMBER r d nd vd ETER OBJECT ∞ PLANE  1 158.64130 10.01750 1.49700 81.6 40.001  2 −273.84120  0.20000 39.683  3 311.49630  3.53260 1.72916 54.7 37.942  4 892.25600  3.34640 37.471  5 −338.49110  3.00000 1.59270 35.4 37.275  6 89.92890  1.04080 34.993  7 93.79050  7.31300 1.80420 46.5 34.954  8 413.43320 VARIABLE 34.549  9 132.04420  4.81280 1.73800 32.3 27.125 10 116030.51080  8.14920 26.498 11 261.40000  2.00000 1.51680 64.2 21.007 12 74.58540  4.43870 19.860 13 −155.90000  2.00000 1.51680 64.2 19.705 14 52.13220  6.50200 18.676 15 −69.52870  2.00000 1.51680 64.2 18.657 16 280.91880  9.84000 19.019 17 140.95680  3.55890 1.67300 38.3 21.626 18 2177.04940 VARIABLE 21.782 (DIAPHRAGM) ∞ 17.71620 22.034 20 182.54690  6.93610 1.49700 81.6 24.712 21 −95.24080  1.72960 24.801 22 −70.16760  2.20000 1.67300 38.3 24.767 23 −145.58000  3.79610 25.266 24 82.38580  7.51860 1.59270 35.4 25.950 25 −367.68210  6.92370 25.745 26 −185.00590  2.20000 1.67300 38.3 24.665 27 87.04700  0.89570 24.890 28 98.30630  9.69560 1.45860 90.2 25.024 29 −85.49430 31.44170 25.260 30 57.90550  2.20000 1.73800 32.3 24.843 31 52.40400 12.77430 24.320 32 −50.03880  2.20000 1.58144 40.7 24.332 33 156.32030  3.92230 26.627 34 −562.03130  5.11250 1.73800 32.3 27.111 35 −109.13710  0.20000 27.736 36 165.56090  9.77870 1.45860 90.2 29.702 37 −92.33720  0.20000 29.994 38 90.64700  8.68520 1.45860 90.2 30.506 39 −479.20080 VARIABLE 30.315 40 ∞ 91.00000 1.51680 64.2 35.000 41 ∞  1.00000 35.000 42 ∞  1.00000 1.47401 65.4 35.000 43 ∞  1.00000 35.000 44 ∞  3.00000 1.50847 61.2 35.000 45 ∞ BF 35.000 IMAGE PLANE ∞

TABLE 9-2 ZOOM RATIO 1.89041 WIDE−ANGLE INTERMEDIATE TELEPHOTO FOCAL LENGTH 87.4243 120.1521 165.2674 F NUMBER 2.48662 2.49963 2.50137 ANGLE OF VIEW 11.3591 8.2581 5.9941 IMAGE HEIGHT 17.3500 17.3500 17.3500 LENS TOTAL 373.7590 373.7504 373.7506 LENGTH BF 1.02465 1.01614 1.01619 d8 2.0000 21.7998 42.6112 d18 49.3474 23.4544 2.0000 d39 16.5087 22.6019 23.2450 ENTRANCE 125.4137 159.0697 195.3564 PUPIL POSITION EXIT PUPIL −1351.3105 −1357.4037 −1358.0468 POSITION FRONT 207.1836 268.5850 340.4934 PRINCIPAL POINT POSITION REAR PRINCIPAL 285.7040 252.4100 206.2398 POINT POSITION

TABLE 9-3 LENS FIRST FOCAL LENS SURFACE LENGTH 1 1 203.6785 2 3 654.6519 3 5 −119.5665 4 7 149.3241 5 9 179.1224 6 11 −202.6817 7 13 −75.3495 8 15 −107.6359 9 17 223.7878 10 20 126.9830 11 22 −203.6607 12 24 114.2662 13 26 −87.6719 14 28 101.3920 15 30 −900.2563 16 32 −64.9375 17 34 182.6430 18 36 130.8168 19 38 167.0194

TABLE 9-4 FRONT REAR LENS LENS PRIN- PRIN- FIRST CONFIG- CIPAL CIPAL SUR- FOCAL URATION POINT POINT GROUP FACE LENGTH LENGTH POSITION POSITION 1 1 205.74848  28.45030  0.04786 9.41976 2 9 −66.17959  43.30160 23.69918 26.14645 3 19 103.81918 136.12630 95.45400 50.65442

TABLE 9-5 LENS GROUP FIRST WIDE- GROUP SURFACE ANGLE INTERMEDIATE TELEPHOTO 1 1 −0.01744 −0.01744 −0.01744 2 9 −0.67236 −0.84167 −1.14464 3 19 −0.61499 −0.67360 −0.67980

The exemplary embodiments have been described above as examples of the technique in the present disclosure. For that purpose, the accompanying drawings and the detailed description have been provided.

The constituent elements illustrated in the accompanying drawings and described in the detailed description may include constituent elements essential for solving the problems, as well as constituent elements that are not essential for solving the problems but required to exemplify the above technique. Therefore, it should not be immediately assumed that the unessential constituent elements are essential constituent elements due to the fact that the unessential constituent elements are described in the accompanying drawings and the detailed description.

Note that the exemplary embodiments described above are provided to exemplify the technique in the present disclosure. Therefore, it is possible to make various changes, replacements, additions, omissions, and the like within the scope of the claims and equivalents thereof.

SUMMARY OF ASPECTS

Hereinafter, various aspects according to the present disclosure will be exemplified.

A first aspect according to the present disclosure is a projection lens system that projects an image of a reduction side into a magnification side. The projection lens system includes a diaphragm, a plurality of positive lenses, and a plurality of negative lenses. In the positive lenses of the projection lens system, a first positive lens that is closer to the magnification side than the diaphragm is and is closest to the diaphragm, a second positive lens that is second closest to the diaphragm after the first positive lens on the magnification side, and a third positive lens that is closer to the reduction side than the diaphragm is and is closest to the diaphragm satisfy following conditions (1) to (3). In the plurality of negative lenses, a first negative lens that is closer to the magnification side than the diaphragm is and is closest to the diaphragm and a second negative lens that is closer to the reduction side than the diaphragm is and is closest to the diaphragm satisfy following conditions (4) to (6). At least one positive lens of the first to third positive lenses satisfies following conditions (7) and (8), Tp1>99%  (1) Tp2>99%  (2) Tp3>99%  (3) Tn1>99%  (4) Tn2>99%  (5) αn1<100×10⁻⁷[/° C.]  (6) dn/dt<−4.5×10⁻⁶  (7) |fp/fw|>1.3  (8)

where

Tp1 indicates an internal transmittance of light having a wavelength of 460 nm when a lens material of the first positive lens has a thickness of 10 mm,

Tp2 indicates an internal transmittance of light having a wavelength of 460 nm when a lens material of the second positive lens has the thickness mentioned above,

Tp3 indicates an internal transmittance of light having a wavelength of 460 nm when a lens material of the third positive lens has the thickness mentioned above,

Tn1 indicates an internal transmittance of light having a wavelength of 460 nm when a lens material of the first negative lens has the thickness mentioned above,

Tn2 indicates an internal transmittance of light having a wavelength of 460 nm when a lens material of the second negative lens has the thickness mentioned above,

αn1 indicates a linear expansion coefficient of the lens material of the first negative lens at room temperature,

dn/dt indicates a temperature coefficient of a relative refractive index of a lens material of the at least one positive lens at room temperature,

fp indicates a focal length of the at least one positive lens, and

fw indicates a focal length at the wide-angle end of a whole system.

According to the projection lens system described above, the first to third positive lenses and the first and second negative lenses that are assumed to be easily affected by heat when the brightness of the image projection device is increased and are assumed to easily affect the performance of the projection lens system satisfy conditions (1) and (8) for reducing the influence of heat. As a result, it is possible to reduce a variation in a projection image due to high brightness of the image projection device and improve the image quality.

According to a second aspect, the projection lens system of the first aspect constitutes a substantially telecentric system on the reduction side. Consequently, it is possible to reduce a color shift in the back lens on the reduction side and the like.

According to a third aspect, in the projection lens system of the first aspect, a number of the positive lenses and the negative lenses is at least 15. According to the projection lens system described above, it is possible to successfully correct various aberrations in the projection lens system.

According to a fourth aspect, in the projection lens system of the first aspect, at least one positive lens of the positive lenses satisfies following condition (9), νp<40  (9)

where

νp indicates an Abbe number of a lens material of the at least one positive lens.

According to the projection lens system described above, by setting the Abbe number of at least one of all positive lenses to be less than the upper limit value of condition (9), it is possible to successfully correct chromatic aberrations while reducing the influence of heat when the brightness is increased. Consequently, it is possible to improve the image quality of the projection image when the brightness is increased.

According to a fifth aspect, in the projection lens system of the first aspect, at least one negative lens of the negative lenses satisfies following condition (10), νn<40  (10)

where

νn indicates an Abbe number of a lens material of the at least one negative lens.

As a result, it is possible to reduce the influence of heat on the negative lens and improve the image quality of the projection image.

According to a six aspect, at least four positive lenses of the positive lenses satisfy following condition (11), dn/dt<−4.5×10⁻⁶  (11)

where

dn/dt indicates a temperature coefficient of a relative refractive index of a lens material of the four positive lenses at room temperature.

As a result, it is possible to reduce the influence of heat by using four or more positive lenses in which the influence of a change in shape due to a local temperature change and the influence of a change in refractive index are offset, and to improve the image quality of the projection image.

According to a seventh aspect, the projection lens system of the first aspect constitutes a zoom lens system including a plurality of lens groups. In the lens groups, a lens group closest to the magnification side has a negative power. The projection lens system satisfies following condition (12), 2<fr/fw<4.5  (12)

where

fr indicates a focal length at a wide-angle end closer to the reduction side than the diaphragm is, and

fw indicates a focal length at the wide-angle end of a whole system.

The projection lens system described above can improve the image quality of the projection image as a negative-lead zoom lens system.

According to an eighth aspect, the projection lens system of the first aspect includes an intermediate imaging position where an image is formed inside the projection lens system. In the projection lens system, a magnification optical system constituted by a plurality of lenses disposed closer to the magnification side than the intermediate imaging position is has a positive power. A relay optical system constituted by a plurality of lenses disposed closer to the reduction side than the intermediate imaging position is has a positive power. The projection lens system satisfies following condition (13), 8<|fr/f|<12  (13)

where

fr indicates a focal length closer to the reduction side than the diaphragm is, and

f indicates a focal length of a whole system.

According to the projection lens system described above, it is possible to improve the image quality of the projection image in a lens system using the intermediate imaging position.

According to a ninth aspect, the projection lens system of the first aspect constitutes a zoom lens system including a plurality of lens groups. In the lens groups, a lens group closest to the magnification side has a positive power. The projection lens system satisfies following condition (14), 0.5<fr/ft<2.0  (14)

where

fr indicates a focal length closer to the reduction side than the diaphragm is, and

ft indicates a focal length at a telephoto end of a whole system.

The projection lens system described above can improve the image quality of the projection image as a positive-lead zoom lens system.

A tenth aspect is an image projection device including the projection lens system of the first aspect and an image forming element that forms an image. The image projection device described above can improve the image quality of an image when the brightness is increased.

INDUSTRIAL APPLICABILITY

The present disclosure is applicable to, for example, an image projection device having a light output of 20,000 lumens or more, and a projection lens system mounted on the image projection device.

REFERENCE MARKS IN THE DRAWINGS

-   -   1 image projection device     -   11 image forming element     -   PL, PL1 to PL9 projection lens system     -   L1 to L22 lens element     -   A diaphragm 

The invention claimed is:
 1. A projection lens system that projects an image of a reduction side into a magnification side, the projection lens system comprising: a magnification optical system; and a relay optical system, wherein: the magnification optical system and the relay optical system include a plurality of lenses, the magnification optical system is disposed closer to the magnification side than the relay optical system is, an intermediate imaging position is located between the magnification optical system and the relay optical system, a lens closest to the reduction side in the magnification optical system has a positive meniscus shape and a convex surface, the convex surface facing the magnification side, a lens closest to the magnification side in the relay optical system has a positive meniscus shape and a convex surface, the convex surface facing the reduction side, a second lens from the magnification side in the relay optical system has a biconcave shape, the relay optical system includes: a diaphragm; a plurality of positive lenses; and a plurality of negative lenses, the diaphragm, the plurality of positive lenses, and the plurality of negative lenses are between the second lens from the magnification side and the reductions side, the plurality of positive lenses include: a first positive lens that is closer to the magnification side than the diaphragm is, and is closest to the diaphragm in the plurality of positive lenses; a second positive lens that is second closest to the diaphragm in the plurality of positive lenses after the first positive lens on the magnification side; and a third positive lens that is closer to the reduction side than the diaphragm is, and is closest to the diaphragm in the plurality of positive lenses, lens materials of the first to third positive lenses satisfy following conditions (1) to (3), respectively, the plurality of negative lenses include: a first negative lens that is closer to the magnification side than the diaphragm is, and is closest to the diaphragm in the plurality of negative lenses; and a second negative lens that is closer to the reduction side than the diaphragm is, and is closest to the diaphragm in the plurality of negative lenses, lens materials of the first and second negative lenses satisfying following conditions (4) to (6), respectively, and at least one positive lens of the first to third positive lenses satisfies following conditions (7) and (8), Tp1>99%  (1) Tp2>99%  (2) Tp3>99%  (3) Tn1>99%  (4) Tn2>99%  (5) αn1<100×10⁻⁷[/° C.]  (6) dn/dt<−4.5×10⁻⁶  (7) |fp/fw|>1.3  (8) where Tp1 indicates an internal transmittance of light having a wavelength of 460 nm measured under a condition that a lens material of the first positive lens has a thickness of 10 mm, Tp2 indicates an internal transmittance of light having a wavelength of 460 nm measured under a condition that a lens material of the second positive lens has a thickness of 10 mm, Tp3 indicates an internal transmittance of light having a wavelength of 460 nm measured under a condition that a lens material of the third positive lens has a thickness of 10 mm, Tn1 indicates an internal transmittance of light having a wavelength of 460 nm measured under a condition that a lens material of the first negative lens has a thickness of 10 mm, Tn2 indicates an internal transmittance of light having a wavelength of 460 nm measured under a condition that a lens material of the second negative lens has a thickness of 10 mm, αn1 indicates a linear expansion coefficient of the lens material of the first negative lens at room temperature, dn/dt indicates a temperature coefficient of a relative refractive index of a lens material of the at least one positive lens at room temperature, fp indicates a focal length of the at least one positive lens, and fw indicates a focal length at a wide-angle end of the projection lens system as a whole.
 2. The projection lens system according to claim 1, wherein the projection lens system constitutes a substantially telecentric system on the reduction side.
 3. The projection lens system according to claim 1, wherein a number of the plurality of positive lenses and the plurality of negative lenses is at least
 15. 4. The projection lens system according to claim 1, wherein the plurality of positive lenses comprise a positive lens that satisfies a following condition (9), νp<40  (9) where νp indicates an Abbe number of a lens material of the positive lens.
 5. The projection lens system according to claim 1, wherein the plurality of negative lenses comprise a negative lens that satisfies a following condition (10), νn<40  (10) where νn indicates an Abbe number of a lens material of the negative lens.
 6. The projection lens system according to claim 1, wherein the projection lens system comprises four positive lenses, each of which satisfies a following condition (11), dn/dt<−4.5×10⁻⁶  (11).
 7. The projection lens system according to claim 1, wherein a second lens from the reduction side in the magnification optical system has a biconvex shape, a third lens from the reduction side in the magnification optical system has a biconcave shape, and a fourth lens from the reduction side in the magnification optical system has a biconvex shape.
 8. The projection lens system according to claim 1, wherein the magnification optical system has a positive power, the relay optical system has a positive power, and the projection lens system satisfies a following condition (13), 8<|fr/fw|<12  (13) where fr indicates a focal length of lenses closer to the reduction side than the diaphragm is.
 9. The projection lens system according to claim 7, wherein a third lens from the magnification side in the relay optical system has a positive meniscus shape and a convex surface, the convex surface facing the reduction side, and a fourth lens from the magnification side in the relay optical system is the second positive lens, the fourth lens having a negative meniscus shape and a convex surface, the convex surface facing the magnification side.
 10. An image projection device comprising: the projection lens system according to claim 1; and an image forming element that forms the image.
 11. A projection lens system that projects an image of a reduction side into a magnification side, the projection lens system comprising: a magnification optical system; and a relay optical system, wherein: the magnification optical system and the relay optical system include a plurality of lenses, the magnification optical system is disposed closer to the magnification side than the relay optical system is, an intermediate imaging position is located between the magnification optical system and the relay optical system, a lens closest to the reduction side in the magnification optical system has a positive meniscus shape and a convex surface, the convex surface facing the magnification side, the relay optical system includes: a diaphragm; a plurality of positive lenses; and a plurality of negative lenses, the diaphragm, the plurality of positive lenses, and the plurality of negative lenses are between the second lens from the magnification side and the reductions side, the plurality of positive lenses include: a first positive lens that is closer to the magnification side than the diaphragm is, and is closest to the diaphragm in the plurality of positive lenses; a second positive lens that is second closest to the diaphragm in the plurality of positive lenses after the first positive lens on the magnification side; and a third positive lens that is closer to the reduction side than the diaphragm is, and is closest to the diaphragm in the plurality of positive lenses, lens materials of the first to third positive lenses satisfy following conditions (1) to (3), respectively, the plurality of negative lenses include: a first negative lens that is closer to the magnification side than the diaphragm is, and is closest to the diaphragm in the plurality of negative lenses; and a second negative lens that is closer to the reduction side than the diaphragm is, and is closest to the diaphragm in the plurality of negative lenses, lens materials of the first and second negative lenses satisfying following conditions (4) to (6), respectively, and at least one positive lens of the first to third positive lenses satisfies following conditions (7) and (8), Tp1>99%  (1) Tp2>99%  (2) Tp3>99%  (3) Tn1>99%  (4) Tn2>99%  (5) αn1<100×10⁻⁷[/° C.]  (6) dn/dt<−4.5×10⁻⁶  (7) |fp/fw|>1.3  (8) where Tp1 indicates an internal transmittance of light having a wavelength of 460 nm measured under a condition that a lens material of the first positive lens has a thickness of 10 mm, Tp2 indicates an internal transmittance of light having a wavelength of 460 nm measured under a condition that a lens material of the second positive lens has a thickness of 10 mm, Tp3 indicates an internal transmittance of light having a wavelength of 460 nm measured under a condition that a lens material of the third positive lens has a thickness of 10 mm, Tn1 indicates an internal transmittance of light having a wavelength of 460 nm measured under a condition that a lens material of the first negative lens has a thickness of 10 mm, Tn2 indicates an internal transmittance of light having a wavelength of 460 nm measured under a condition that a lens material of the second negative lens has a thickness of 10 mm, αn1 indicates a linear expansion coefficient of the lens material of the first negative lens at room temperature, dn/dt indicates a temperature coefficient of a relative refractive index of a lens material of the at least one positive lens at room temperature, fp indicates a focal length of the at least one positive lens, and fw indicates a focal length at a wide-angle end of the projection lens system as a whole. 